rally leaving stale opened files in ssh module

We are creating instance for SSH class and calling _wait_for_ssh function i.e

ssh = sshutils.SSH(user, ip, password=password)
self._wait_for_ssh(ssh, timeout=timeout, interval=interval)

and this will be successful after some attempts

2022-01-10 07:30:28.951 98870 RALLYDEBUG rally.utils.sshutils [-] Ssh is still unavailable: SSHError("Exception <class 'socket.timeout'> was raised during connect to root@172.31.11.67:22. Exception value is: timeout('timed out',)",)
2022-01-10 07:30:34.957 98870 RALLYDEBUG rally.utils.sshutils [-] Ssh is still unavailable: SSHError("Exception <class 'socket.timeout'> was raised during connect to root@172.31.11.67:22. Exception value is: timeout('timed out',)",)
...
...
...
2022-01-10 07:33:36.220 98870 RALLYDEBUG rally.utils.sshutils [-] stdout: b'Linux\n'

However we can see many FIFO files (through lsof command) opened by rally
cat log_lsof | grep rally | wc -l
4440581
cat log_lsof | grep rally | grep FIFO | wc -l
2564483
cat log_lsof | grep rally | grep IPv4 | wc -l
1252151

Because of this our workloads are unable to connect to OSP endpoints and failing with below errors

2022-01-10 09:12:48.903 98897 ERROR rally.task.runner [-] Iteration 257 raised Exception: keystoneauth1.exceptions.connection.ConnectFailure: Unable to establish connection to http://172.18.0.111:9696/v2.0/routers: HTTPConnectionPool(host='172.18.0.111', port=9696): Max retries exceeded with url: /v2.0/routers (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f4ea85ed9b0>: Failed to establish a new connection: [Errno 24] Too many open files',))
2022-01-10 09:12:48.903 98897 ERROR rally.task.runner Traceback (most recent call last):
2022-01-10 09:12:48.903 98897 ERROR rally.task.runner File "/home/stack/browbeat/.rally-venv/lib/python3.6/site-packages/urllib3/connection.py", line 175, in _new_conn
2022-01-10 09:12:48.903 98897 ERROR rally.task.runner File "/home/stack/browbeat/.rally-venv/lib/python3.6/site-packages/urllib3/util/connection.py", line 96, in create_connection
2022-01-10 09:12:48.903 98897 ERROR rally.task.runner File "/home/stack/browbeat/.rally-venv/lib/python3.6/site-packages/urllib3/util/connection.py", line 77, in create_connection
2022-01-10 09:12:48.903 98897 ERROR rally.task.runner File "/usr/lib64/python3.6/socket.py", line 144, in __init__
2022-01-10 09:12:48.903 98897 ERROR rally.task.runner OSError: [Errno 24] Too many open files

We observed that "def execute" [1] method opening stdout and stderr and never closing them. Comments [2] in the function says it has to return stdout and stderr, however they are returning stdout.read(), stderr.read(). So the user can't call stdout.close and stderr.close.

If an exception happens in run()[3] (this is happend in our case i.e previous log messages) user can never close stdin and stdout leaving them stale.

[1] https://github.com/openstack/rally/blob/master/rally/utils/sshutils.py#L240
[2] https://github.com/openstack/rally/blob/master/rally/utils/sshutils.py#L247
[3] https://github.com/openstack/rally/blob/master/rally/utils/sshutils.py#L252