Scan: Stop scan restart after exiting group

If the user enters a group before the end of a medialibrary scan, the
boolean scanNeeded is set to true in onStop. To stop the scan from
happening when coming back from the group, scanNeeded is set to false in
onActivityResult.

Closes #2255

application/vlc-android/src/org/videolan/vlc/gui/MainActivity.kt

@@ -236,6 +236,8 @@ class MainActivity : ContentActivity(),
         } else if (requestCode == ACTIVITY_RESULT_SECONDARY) {
             if (resultCode == RESULT_RESCAN) {
                 forceRefresh(currentFragment)
+            } else {
+                scanNeeded = false
             }
         }
     }