LU-13990 ldlm: ldlm_flock_deadlock() ASSERTION(req != lock) failed

LU-13990 ldlm: ldlm_flock_deadlock() ASSERTION(req != lock) failed

A client gets evicted and reconnects, so there can be a window
with 2 exports with flocks from the same client.
In this case during deadlock search from the new export we can go
to the old export and back to the new one.

Failed exports should be excluded from
deadlock search.

Change-Id: I9dec50d4c6694bbbcf13b976b5ebdc29377261ce
HPE-bug-id: LUS-8635
Signed-off-by: Andriy Skulysh <c17819@cray.com>
Reviewed-by: Alexander Boyko <c17825@cray.com>
Reviewed-by: Vitaly Fertman <c17818@cray.com>
Reviewed-on: https://review.whamcloud.com/40047
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Vitaly Fertman <vitaly.fertman@hpe.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>