LU-12296 llite: improve ll_dom_lock_cancel

LU-12296 llite: improve ll_dom_lock_cancel

ll_dom_lock_cancel() should zero kms attribute similar to
mdc_ldlm_blocking_ast0().

In order to avoid code duplication between mdc_ldlm_blocking_ast0()
and ll_dom_lock_cancel() - add cl_object_operations method to be able
to reach mdc's blocking ast from llite level.

Test illustrating the issue is added.

Cray-bug-id: LUS-7118
Signed-off-by: Vladimir Saveliev <c17830@cray.com>
Change-Id: I2b100ead6d420dbf561bc61be973d64dad317214
Reviewed-on: https://review.whamcloud.com/34858
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>