gluster: fix vdsmapi gluster json schema error

Updates schema file for task info, task summary
and fixes the schema error.

Change-Id: I29a011bd6434e0524f7a4cdefcfa599e8c90c74f
Signed-off-by: Timothy Asir <tjeyasin@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/21755
Reviewed-by: Dan Kenigsberg <danken@redhat.com>