auth-cfg-wrapper: Fix memory leak with hash-and-URL certificates

We wrap the auth-cfg object and its contents, so there is no need to get
an additional reference for the enumerated certificate.

Fixes a44bb9345f ("merged multi-auth branch back into trunk")

src/libstrongswan/credentials/sets/auth_cfg_wrapper.c

@@ -108,7 +108,7 @@ static bool fetch_cert(wrapper_enumerator_t *enumerator,
 	}
 	*value = cert;
 	enumerator->auth->replace(enumerator->auth, enumerator->inner,
-							  *rule, cert->get_ref(cert));
+							  *rule, cert);
 	return TRUE;
 }