LU-1882 llite: Adding timed wait in ll_umount_begin

LU-1882 llite: Adding timed wait in ll_umount_begin

There exists timing race between umount and other
thread which will increment the reference count on
mnt e.g. getattr. If umount thread lose the race
then umount fails with EBUSY error. To avoid this
timed wait is added so that umount thread will wait
for user to decrement the mnt reference count.

This patch also fixes below two problems
1.the fail_loc code in conf-sanity test 45 to
OR with the OBD_FAIL_ONCE (0x80000000) to prevent
the fail_loc from looping forever.

2.fixes the fail_loc code name from
OBD_FAIL_PTLRPC_LONG_UNLINK to
OBD_FAIL_PTLRPC_LONG_REPL_UNLINK.

Signed-off-by: Rahul Deshmukh <rahul.deshmukh@seagate.com>
Signed-off-by: Lokesh Nagappa Jaliminche <lokesh.jaliminche@seagate.com>
Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: Icab9b560cadcb8623c8592bfc4c5a842277ad266
Seagate-bug-id: MRP-1192
Reviewed-on: http://review.whamcloud.com/20061
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>