LU-17325 o2iblnd: CM_EVENT_UNREACHABLE on established conn

LU-17325 o2iblnd: CM_EVENT_UNREACHABLE on established conn

There were examples in the field with RoCE setups which demonstrate
that CM_EVENT_UNREACHABLE may be received when connection is already
in ESTABLISHED state. This causes an assert in kiblnd_cm_callback to
fail.

Handle this in a more gracious manner: report the event as unexpected
and allow the flow to continue. If there are indeed issues on
the connection, it is expected to report transaction errors later
and get cleaned up without crashing the whole system.

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Change-Id: If32166fe9fc59e025609c2035cb1c03d3bed22f2