xfs: shorten the shutdown messages to a single line

Consolidate the shutdown messages to a single line containing the
reason, the passed-in flags, the source of the shutdown, and the end
result.  This means we now only have one line to look for when
debugging, which is useful when the fs goes down while something else is
flooding dmesg.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>