Allow rediscovery of hosts after deletion without having to force quit the app

Limelight/Network/DiscoveryManager.h

@@ -21,6 +21,7 @@
 - (void) startDiscovery;
 - (void) stopDiscovery;
 - (void) stopDiscoveryBlocking;
+- (void) resetDiscoveryState;
 - (BOOL) addHostToDiscovery:(TemporaryHost*)host;
 - (void) removeHostFromDiscovery:(TemporaryHost*)host;
 - (void) discoverHost:(NSString*)hostAddress withCallback:(void (^)(TemporaryHost*, NSString*))callback;