qemu: Unref cfg in qemuDomainDefPostParse

Introduced by commit 15ad2ecf.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>
(cherry picked from commit d3d4fb4b)

src/qemu/qemu_domain.c

@@ -1464,6 +1464,7 @@ qemuDomainDefPostParse(virDomainDefPtr def,
     ret = 0;
  cleanup:
     virObjectUnref(qemuCaps);
+    virObjectUnref(cfg);
     return ret;
 }