Remove trivial GScan logs

These helped once; but now this is just noise. Also
given that GMSCore starts/stops scans many times it is
taking too much of log real estate.

Bug: 20416721

Change-Id: I965ed919afbac56e123e8d019be84d7d33abf3f9

wifi/java/android/net/wifi/WifiScanner.java

@@ -1007,7 +1007,7 @@ public class WifiScanner {
                             ((ParcelableScanResults) msg.obj).getResults());
                     return;
                 case CMD_SINGLE_SCAN_COMPLETED:
-                    Log.d(TAG, "removing listener for single scan");
+                    if (DBG) Log.d(TAG, "removing listener for single scan");
                     removeListener(msg.arg2);
                     break;
                 default: