xfs: simplify log shutdown checking in xfs_log_release_iclog

There is no need to check for the ioerror state before the lock, as
the shutdown case is not a fast path.  Also remove the call to force
shutdown the file system, as it must have been shut down already
for an iclog to be in the ioerror state.  Also clean up the flow of
the function a bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>