qemu_process: Resolve Coverity RESOURCE_LEAK

If virSecurityManagerClearSocketLabel() fails, 'agent' won't
be freed before jumping to cleanup.

Signed-off-by: Wang Rui <moon.wangrui@huawei.com>

src/qemu/qemu_process.c

@@ -264,6 +264,7 @@ qemuConnectAgent(virQEMUDriverPtr driver, virDomainObjPtr vm)
                                            vm->def) < 0) {
         VIR_ERROR(_("Failed to clear security context for agent for %s"),
                   vm->def->name);
+        qemuAgentClose(agent);
         goto cleanup;
     }