tvhlog: added build define to remove logging thread.

I think eventually I'll make this is cmdline switch so I can turn it on if
I need it.
subscription: fix double list insertion on detection of bad service

If a service was marked as bad (no input) it was not unlinking the
subscription from the service before re-applying, this resulted in
a double entry into the service subs list and ultimatey a livelock
or possibly worse.