Fix dump_cib for corosync provider

W/o this patch, dump_cib sometimes may
return an empty xml

Related-bug: #1375842

Change-Id: Ia2dafe173f03bce82757d6e9522b405fb0969fb4
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
Merge "Fix dump_cib for corosync provider"