ahc: correct error message

The error message is specific to only one of the failure cases and is
misleading in the others. Correct it to be more generic and cover all
the failure cases.

https://bugzilla.gnome.org/show_bug.cgi?id=763065

sys/androidmedia/gst-android-hardware-camera.c

@@ -1681,7 +1681,8 @@ _init_classes (void)
 
 failed:
   if (err) {
-    GST_ERROR ("Failed to get android.hardware.Camera class: %s", err->message);
+    GST_ERROR ("Failed to initialize android.hardware.Camera classes: %s",
+        err->message);
     g_clear_error (&err);
   }