DB is no longer recreated for individual tests

When running individual Nova tests or suites the database is no longer being initialized properly...

Trying to run a random libvirt tests fails with the following exception:

[dprince@dovetail nova]$ ./run_tests.sh test_libvirt:NWFilterTestCase.test_unfilter_instance_undefines_nwfilters

NWFilterTestCase
    test_unfilter_instance_undefines_nwfilters ERROR 0.22

======================================================================
ERROR: test_unfilter_instance_undefines_nwfilters (test_libvirt.NWFilterTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/dprince/projects/nova/nova/tests/test_libvirt.py", line 3192, in test_unfilter_instance_undefines_nwfilters
    instance_ref = self._create_instance()
  File "/home/dprince/projects/nova/nova/tests/test_libvirt.py", line 3096, in _create_instance
    'instance_type_id': 1})
  File "/home/dprince/projects/nova/nova/db/api.py", line 563, in instance_create
    return IMPL.instance_create(context, values)
  File "/home/dprince/projects/nova/nova/db/sqlalchemy/api.py", line 131, in wrapper
    return f(*args, **kwargs)
  File "/home/dprince/projects/nova/nova/db/sqlalchemy/api.py", line 1399, in instance_create
    security_groups)
  File "/home/dprince/projects/nova/nova/db/sqlalchemy/api.py", line 1386, in _get_sec_group_models
    session=session)
  File "/home/dprince/projects/nova/nova/db/sqlalchemy/api.py", line 3477, in security_group_ensure_default
    columns_to_join=[], session=session)
  File "/home/dprince/projects/nova/nova/db/sqlalchemy/api.py", line 131, in wrapper
    return f(*args, **kwargs)
  File "/home/dprince/projects/nova/nova/db/sqlalchemy/api.py", line 3406, in security_group_get_by_name
    result = query.first()
  File "/home/dprince/projects/nova/.venv/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 2156, in first
    ret = list(self[0:1])
  File "/home/dprince/projects/nova/.venv/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 2023, in __getitem__
    return list(res)
  File "/home/dprince/projects/nova/.venv/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 2227, in __iter__
    return self._execute_and_instances(context)
  File "/home/dprince/projects/nova/.venv/lib/python2.7/site-packages/sqlalchemy/orm/query.py", line 2242, in _execute_and_instances
    result = conn.execute(querycontext.statement, self._params)
  File "/home/dprince/projects/nova/.venv/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1449, in execute
    params)
  File "/home/dprince/projects/nova/.venv/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1584, in _execute_clauseelement
    compiled_sql, distilled_params
  File "/home/dprince/projects/nova/.venv/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1698, in _execute_context
    context)
  File "/home/dprince/projects/nova/.venv/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 1691, in _execute_context
    context)
  File "/home/dprince/projects/nova/.venv/lib/python2.7/site-packages/sqlalchemy/engine/default.py", line 331, in do_execute
    cursor.execute(statement, parameters)
OperationalError: (OperationalError) no such table: security_groups u'SELECT security_groups.created_at AS security_groups_created_at, security_groups.updated_at AS security_groups_updated_at, security_groups.deleted_at AS security_groups_deleted_at, security_groups.deleted AS security_groups_deleted, security_groups.id AS security_groups_id, security_groups.name AS security_groups_name, security_groups.description AS security_groups_description, security_groups.user_id AS security_groups_user_id, security_groups.project_id AS security_groups_project_id \nFROM security_groups \nWHERE security_groups.deleted = ? AND security_groups.project_id = ? AND security_groups.name = ?\n LIMIT ? OFFSET ?' (0, 'fake', 'default', 1, 0)
-------------------- >> begin captured stdout << ---------------------
NWFilterTestCase: Setup called

--------------------- >> end captured stdout << ----------------------
-------------------- >> begin captured logging << --------------------
nova.common.deprecated: WARNING: Deprecated Config: The root_helper option (which lets you specify a root wrapper different from nova-rootwrap, and defaults to using sudo) is now deprecated. You should use the rootwrap_config option instead.
--------------------- >> end captured logging << ---------------------

Slowest 1 tests took 0.22 secs:
    0.22 NWFilterTestCase.test_unfilter_instance_undefines_nwfilters
----------------------------------------------------------------------
Ran 1 test in 0.227s

FAILED (errors=1)

------

We should support running individual tests that require use of the SQLite database.