LU-14027 ldlm: Do not hang if recovery restarted during lock replay

LU-14027 ldlm: Do not hang if recovery restarted during lock replay

LU-13600 introduced lock ratelimiting logic, but it did not take
into account that if there's a disconnection in the REPLAY_LOCKS
phase then yet unsent locks get stuck in the sending queue so
the replay locks thread hangs with imp_replay_inflight elevated
above zero.

The direct consequence from that is recovery state machine never
advances from REPLAY to REPLAY_LOCKS status when imp_replay_inflight
is non zero.

Adjust __ldlm_replay_locks() to check if the import state changed
before attempting to send any more requests.

Add a testcase.

Change-Id: Idbaf5461f33d1884088269d67d01071c7e1bf8a5
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Fixes: 3b613a442b ("LU-13600 ptlrpc: limit rate of lock replays")
Reviewed-on: https://review.whamcloud.com/40238
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>