cli: Fix 'status all' xml output when volumes are not started

CLI now only outputs one XML document for 'status all' only containing
those volumes which are started.

BUG: 1004218
Change-Id: Id4130fe59b3b74475d8bd1cc8134ac59a28f1b7e
Signed-off-by: Kaushal M <kaushal@redhat.com>
Reviewed-on: http://review.gluster.org/5773
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>