Fixes animation video from not playing after onStop

Adds a pause command that doesn't destroy the video surface, and calls
onStop when we want to destroy the media player.

bug:26516460
Change-Id: If46d26088e81fdca6a73a663a48901bb5245acc8

src/com/android/settings/fingerprint/FingerprintEnrollFindSensor.java

@@ -59,6 +59,12 @@ public class FingerprintEnrollFindSensor extends FingerprintEnrollBase {
     @Override
     protected void onStop() {
         super.onStop();
+        mAnimation.pauseAnimation();
+    }
+
+    @Override
+    protected void onDestroy() {
+        super.onDestroy();
         mAnimation.stopAnimation();
     }