Use less CPU while waiting for human player to move

After the engine plays a move in a game, a thread could get into a
state where it would poll for engine output every millisecond while
waiting for the human player to make the next move.

Even though this was not a busy wait, it would still use more CPU
resources than necessary, so the logic has been changed to prevent
this situation.

DroidFishApp/src/main/java/org/petero/droidfish/engine/DroidComputerPlayer.java

@@ -925,7 +925,8 @@ public class DroidComputerPlayer {
     }
 
     private synchronized int getReadTimeout() {
-        boolean needGuiUpdate = depthModified || currMoveModified || pvModified || statsModified;
+        boolean needGuiUpdate = (searchRequest != null && searchRequest.currPos != null) &&
+            (depthModified || currMoveModified || pvModified || statsModified);
         int timeout = 2000000000;
         if (needGuiUpdate) {
             long now = System.currentTimeMillis();