rpc: daemon: Fix virtlog/virtlock daemon reload

rpc: daemon: Fix virtlog/virtlock daemon reload

Trying to reload/SIGUSR1 virtlogd or virtlockd fails with:

error : virNetDaemonRun:747 : internal error: Not all servers restored, cannot run server

Commit 252610f7 changed the daemon state json to allow tracking
multiple servers. However it missed clearing dmn->srvObject after
the json is empty, like the previous code paths handled.  Later on in
virNewDaemonRun, dmn->srvObject is expected to be empty otherwise we
throw the above error.

https://bugzilla.redhat.com/show_bug.cgi?id=1311013
(cherry picked from commit 9b69f02243f2abec4170576dfe28f8a4bb398b4e)