conf/domain_capabilities: fix resource leak

Commit 14319c81 introduced CPU host model in domain capabilities
and the *hostmodel* variable is always filled by virCPUDefCopy()
and needs to be freed.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>
(cherry picked from commit 87d97a9d)

src/conf/domain_capabilities.c

@@ -82,6 +82,7 @@ virDomainCapsDispose(void *obj)
     VIR_FREE(caps->path);
     VIR_FREE(caps->machine);
     virObjectUnref(caps->cpu.custom);
+    virCPUDefFree(caps->cpu.hostModel);
 
     virDomainCapsStringValuesFree(&caps->os.loader.values);
 }