staging: lustre: statahead: lock leaks if statahead file recreated

During statahead file may be recreated, though this is rare case,
current code will leak the lock, this patch will release lock in
this case.

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-7232
Reviewed-on: http://review.whamcloud.com/16841


Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>