storage/posix: Treat ENODATA/ENOATTR as success in bulk removexattr

        Backport of http://review.gluster.org/9049

Bulk remove xattr is internal fop in gluster. Some of the xattrs may have
special behavior. Ex: removexattr("posix.system_acl_access"), removes more than
one xattr on the file that could be present in the bulk-removal request.
Removexattr of these deleted xattrs will fail with either ENODATA/ENOATTR.
Since all this fop cares is removal of the xattrs in bulk-remove request and
if they are already deleted, it can be treated as success.

BUG: 1163571
Change-Id: I009f4736f8b6362d7115f57a7d7aece74e56e4f6
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/9109
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>