do not subtract max priority from jack RT priority

This subtraction (a) can create negative values (b) doesn't make any sense since we just add 10 to the jack priority later.

zalsa/jackclient.cc

@@ -70,7 +70,7 @@ void Jackclient::init (const char *jserv)
        register_ports (_nchan);
     }
 
-    _rprio = jack_client_real_time_priority (_client) -  sched_get_priority_max (spol);
+    _rprio = jack_client_real_time_priority (_client);
 }
 
 void Jackclient::register_ports (int n)