libxenstat: always free qmp_stats

libxenstat: always free qmp_stats

Originally qmp_stats is only freed in failure path and leaked in success
path.

Instead of wiring up the success path, rearrange the code a bit to
always free qmp_stats before checking if info is NULL.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Charles Arnold <carnold@suse.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>