factory reset: restore ext4 policy on /data/cache

If ext4 policy is not restored, system won't boot properly
after a factory reset.

When /data is formatted by the user, we need to make sure we
do not create the /data/cache directory so that Android can
create it with the new policy for /data.

This also removes extraneous umount calls, and places them
in the specific wipe function for each filesystem.

Change-Id: I71ff39d8660fbf4aa6fe8a8309e291166359da72
diff --git a/.gitignore b/.gitignore
index e03babb..480f547 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 .*.swp
 *~
 tags
+.vscode