eCryptFS: fix imbalanced mutex locking

Fix imbalanced calls for mutex lock/unlock on ecryptfs_daemon_hash_mux
Revealed by Ingo Molnar: http://lkml.org/lkml/2008/5/7/260

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>