cli: Address a double free with volume info.

Crash is observed when volume info is performed on a
non-exisiting volume name and the output format is xml.

Change-Id: I88aa5d9dc954b1352f5cc3b5b38742c832bc1bb8
BUG: 949298
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/4785
Reviewed-by: Kaushal M <kaushal@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>