posix-acl: check dictionary before using it

If extended attributes are not present in md-cache it returns NULL as xattr.
posix acl xlator should check for NULL before using xattr.

If normal and default ACLs are not set on file then md-cache will not contain
system.posix_acl_access and system.posix_acl_default extended attributes in
its cache.

Therefore posix_acl_lookup_cbk should check xattr before using it, otherwise
the logs will get filled with dictionary errors.

> Reviewed-on: http://review.gluster.org/15769
> Reviewed-by: Raghavendra Talur <rtalur@redhat.com>
> Smoke: Gluster Build System <jenkins@build.gluster.org>
> Reviewed-by: jiffin tony Thottan <jthottan@redhat.com>
> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
> Reviewed-by: Vijay Bellur <vbellur@redhat.com>
> CentOS-regression: Gluster Build System <jenkins@build.gluster.org>

(cherry picked from commit de7fe24663713fff364cfc2b52b675e3e979ee68)

Change-Id: Icebf73cf0b313bd3e82ca8cbda63786dd0fa47da
BUG: 1392869
Signed-off-by: Rajesh Joseph <rjoseph@redhat.com>
Reviewed-on: http://review.gluster.org/15801
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Raghavendra Talur <rtalur@redhat.com>

0 files changed, 0 insertions, 0 deletions