NFS4: Trace state recovery operation

[ Upstream commit 511ba52e ]

Add a trace point in the main state manager loop to observe state
recovery operation. Help track down state recovery bugs.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Stable-dep-of: ed1cc05a ("NFSv4: Fix a nfs4_state_manager() race")
Signed-off-by: Sasha Levin <sashal@kernel.org>