glusterd: Coverity fix for going out of scope leaks of directory pointer

In function volgen_apply_filters() directory stream associated with
"filterdir" should be close after opening directory stream corresponding
to directory name. closedir() also closes the underlying file descriptor
associated with "filterdir".

Coverity CID: 1124723

Change-Id: I78ed04047ded98bf95d201afed01c727aa506882
BUG: 789278
Reviewed-on: http://review.gluster.org/8088
Reviewed-by: Atin Mukherjee <amukherj@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaushal M <kaushal@redhat.com>