[RenderScript] Interrupt mMessageThread when tearing down context.

- Interrupt mMessageThread, so it gets to see immediately
    that mRun is false and exit rightaway.

Change-Id: Ic586ef225a5c6f3a77f89de00b7fb3f3547c9838

rs/java/android/renderscript/RenderScript.java

@@ -1616,6 +1616,9 @@ public class RenderScript {
 
             nContextDeinitToClient(mContext);
             mMessageThread.mRun = false;
+            // Interrupt mMessageThread so it gets to see immediately that mRun is false
+            // and exit rightaway.
+            mMessageThread.interrupt();
 
             // Wait for mMessageThread to join.  Try in a loop, in case this thread gets interrupted
             // during the wait.  If interrupted, set the "interrupted" status of the current thread.