Reset command line flags default values in Android (#128)

As flags are global variables, any change to them will survive
an exit of function android_main(), so we cannot rely on their
value to be set to default when android_main() is called again.

vulkan-worker/src/android/src/main/cpp/main.cc

@@ -136,10 +136,15 @@ void FreeGflagsArgs(int argc, char **argv) {
 
 void android_main(struct android_app* state) {
 
-  // New default values
+  // Reset all default values, as any change may survive the exiting of this
+  // android_main() function and still be set when android_main() is called
+  // again.
   FLAGS_sanity_before = "/sdcard/graphicsfuzz/sanity_before.png";
   FLAGS_sanity_after = "/sdcard/graphicsfuzz/sanity_after.png";
   FLAGS_png_template = "/sdcard/graphicsfuzz/image";
+  FLAGS_info = false;
+  FLAGS_skip_render = false;
+  FLAGS_num_render = 3;
 
   int argc = 0;
   char **argv = nullptr;