better link state detection

Currently _is_active_nic performs multiple checks to see if a link is live.

However some hardware, e.g. Lenovo x3850 x6, has a built-in Ethernet over USB device which reports as follows:

2: enp0s29u1u1u5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
    inet 169.254.95.120/24 brd 169.254.95.255 scope link dynamic enp0s29u1u1u5
       valid_lft 356sec preferred_lft 356sec
    inet6 fe80::xx:xxxx:xxxx:xxxx/64 scope link
       valid_lft forever preferred_lft forever

Ethtool further reports the link as active:

[root@overcloud-controller-1 heat-admin]# ethtool enp0s29u1u1u5
Settings for enp0s29u1u1u5:
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: yes

This breaks the automatic naming convention in tripleo where nic1, nic2 etc is used and results in a failed deployment.

This nic passes the above tests in that it is:

a) not named lo
b) has a device subdir
c) reports having a carrier signal
d) reports having an address, albeit a link-local/169 address

I am therefore proposing that the carrier test be changed to check operstate for UP.

Patch to follow.