Prevent realtime scheduling for ad-hoc acceptors

I noticed that there were some realtime adhoc-acceptors running on my
system. That should of course not happen, since these only exist to
catch some sporadic (and likely as a result of a badly behaving plugin)
mutual recursion on the audio thread.

src/common/communication/common.h

@@ -780,6 +780,9 @@ class AdHocSocketHandler {
         Thread secondary_requests_handler([&]() {
             pthread_setname_np(pthread_self(), "adhoc-acceptor");
 
+            // Any secondary threads should not be realtime
+            set_realtime_priority(false);
+
             secondary_context.run();
         });