make tar backups opt in.

Change-Id: Ib01131f3a65ce4114e73abe2c7ba42263d281844
diff --git a/extendedcommands.c b/extendedcommands.c
index b32ca0b..4395377 100644
--- a/extendedcommands.c
+++ b/extendedcommands.c
@@ -1105,9 +1105,9 @@
 
 void process_volumes() {
     create_fstab();
-    if (volume_for_path("/sdcard") == NULL) {
-        rmdir("/sdcard");
-        symlink("/data/media", "/sdcard");
+
+    if (is_data_media()) {
+        setup_data_media();
     }
 
     return;