qemu: reset await_event in all error paths in qemuAgentCommand

A fixup to patch [1]. We need to reset await_event in all
error paths.

[1] 52532073 : qemu: remove redundant needReply argument of qemuAgentCommand
Signed-off-by: NNikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_agent.c

@@ -1113,7 +1113,7 @@ qemuAgentCommand(qemuAgentPtr agent,
     }
 
     if (qemuAgentGuestSync(agent) < 0)
-        return -1;
+        goto cleanup;
 
     if (!(cmdstr = virJSONValueToString(cmd, false)))
         goto cleanup;