autofs: fix careless error in recent commit

Commit ecc0c469 ("autofs: don't fail mount for transient error") was
meant to replace an 'if' with a 'switch', but instead added the 'switch'
leaving the case in place.

Link: http://lkml.kernel.org/r/87zi6wstmw.fsf@notabene.neil.brown.name
Fixes: ecc0c469

 ("autofs: don't fail mount for transient error")
Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: NeilBrown <neilb@suse.com>
Cc: Ian Kent <raven@themaw.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>