nvme-rdma: fix concurrent reset and reconnect

Now ctrl state machine allows to transition from RESETTING to
RECONNECTING.  In nvme-rdma when we receive a rdma cm DISONNECTED event,
we trigger nvme_rdma_error_recovery. This happens also when we execute a
controller reset, issue a cm diconnect request and receive a cm
disconnect reply, as a result, the reset work and the error recovery work
can run concurrently.

Until now the state machine prevented from the error recovery work from
running as a result of a controller reset (RESETTING -> RECONNECTING was
not allowed).

To fix this, we adopt the FC state machine approach, we always transition
from LIVE to RESETTING and only then to RECONNECTING.  We do this both
for the error recovery work and the controller reset work:

 1. transition to RESETTING
 2. teardown the controller association
 3. transition to RECONNECTING

This will restore the protection against reset work and error recovery work
from concurrently running together.

Fixes: 3cec7f9d

 ("nvme: allow controller RESETTING to RECONNECTING transition")
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>