This patch removes ll_md_blocking_ast() processing for
not granted locks. The reason is ll_invalidate_negative_children()
can slow down I/O significantly without a reason if there
are thousands or millions of files in the directory
cache.

Change-Id: Ic69c5f02f71c14db4b9609677d102dd2993f4feb
Seagate-bug-id: MRP-3409
Signed-off-by: Andrew Perepechko <c17827@cray.com>
Reviewed-on: https://review.whamcloud.com/19665


Tested-by: Jenkins
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>