Set GID required to write, media_rw mount point.

Add sdcard FUSE daemon flag to specify the GID required for a package
to have write access.  Normally sdcard_rw, but it will be media_rw
for secondary external storage devices, so DefaultContainerService
can still clean up package directories after uninstall.

Create /mnt/media_rw which is where vold will mount raw secondary
external storage devices before wrapping them in a FUSE instance.

Bug: 10330128, 10330229
Change-Id: I4385c36fd9035cdf56892aaf7b36ef4b81f4418a
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 8150a73..86e124f 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -61,6 +61,7 @@
 
     # See storage config details at http://source.android.com/tech/storage/
     mkdir /mnt/shell 0700 shell shell
+    mkdir /mnt/media_rw 0700 media_rw media_rw
     mkdir /storage 0751 root sdcard_r
 
     # Directory for putting things only root should see.