LU-7927 llite: Deadlock between ll_setattr and write/ll_fsync

LU-7927 llite: Deadlock between ll_setattr and write/ll_fsync

The patch http://review.whamcloud.com/10013 (commit 85bd36cc695)
"LU-4840 lfs: Use file lease to implement migration" moves
lli_trunc_sem into vvp layer.  It violates lli_trunc_sem/i_mutex
locking order.  So i_mutex should be taken after lli_trunc_sem now.

Change-Id: I2ecd52b7ae6eca74c6db7d94b1de1333560bc45d
Seagate-bug-id: MRP-3372
Signed-off-by: Andriy Skulysh <andriy.skulysh@seagate.com>
Reviewed-on: http://review.whamcloud.com/19165
Reviewed-by: Patrick Farrell <paf@cray.com>
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Ann Koehler <amk@cray.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>