LU-3889 osc: Allow lock to be canceled at ENQ time

LU-3889 osc: Allow lock to be canceled at ENQ time

A cl_lock can be canceled when it's in CLS_ENQUEUED state.
We can't unuse this kind of lock in lov_lock_unuse() because
it will bring this lock into CLS_NEW state and then confuse
osc_lock_upcall().

Add a regression test case by Alexander Boyko.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Signed-off-by: Alexander Boyko <alexander_boyko@xyratex.com>
Change-Id: Ieb9209203a363c9098b9ea4637a9d12e12ef1aa4
Reviewed-on: http://review.whamcloud.com/8717
Tested-by: Jenkins
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>