LU-1842 ldlm: support for sending GL ASTs to multiple locks

LU-1842 ldlm: support for sending GL ASTs to multiple locks

Traditionally, a glimpse callback is sent to one single lock which
is the highest PW extent lock.
The new quota code uses glimpse callbacks in a different manner since
it can issue multiple glimpse ASTs to different slaves (as done for
blocking callbacks for instance) to notify those latters of the new
qunit value.

This patch modifies the glimpse callback path to use
ldlm_run_ast_work() to issue multiple glimpse ASTs in one shot (as
done currently for other lock callbacks).

Signed-off-by: Johann Lombardi <johann@whamcloud.com>
Change-Id: I972630fcf3158dd1d361392913f8086f1ebaa39f
Reviewed-on: http://review.whamcloud.com/3887
Reviewed-by: Niu Yawei <niu@whamcloud.com>
Tested-by: Hudson
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>