LU-13600 ptlrpc: re-enterable signal_completed_replay()

LU-13600 ptlrpc: re-enterable signal_completed_replay()

The signal_completed_replay() can meet race conditions while
checking imp_replay_inflight counter, so remove assertion and
check race conditions instead.

Fixes: 3b613a442b ("LU-13600 ptlrpc: limit rate of lock replays")
Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Change-Id: Ib7c372b1757556b7285f380b40167742f9b71ec6
Reviewed-on: https://review.whamcloud.com/39140
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>