Bind mount install and android writable DATA and OBB dirs

To improvement performance, and also making them able to list
the dirs.

This should also be fine under b/151055432, as the whole obb
directory is mounted, renameTo() from installer to apps should be
a move not copy.

Bug: 153422990
Bug: 153540919
Test: atest AdoptableHostTest
Change-Id: Ia18fd4393db14a0f11d6e5b947dd716515bdeeef
diff --git a/VolumeManager.cpp b/VolumeManager.cpp
index e4e5781..eac020f 100644
--- a/VolumeManager.cpp
+++ b/VolumeManager.cpp
@@ -947,7 +947,7 @@
              !StartsWith(test, "/mnt/scratch") &&
 #endif
              !StartsWith(test, "/mnt/vendor") && !StartsWith(test, "/mnt/product") &&
-             !StartsWith(test, "/mnt/installer")) ||
+             !StartsWith(test, "/mnt/installer") && !StartsWith(test, "/mnt/androidwritable")) ||
             StartsWith(test, "/storage/")) {
             toUnmount.push_front(test);
         }