vold: Don't unmount /mnt/installer on start.

This is a slave bind mount of /mnt/user, created before we create the
two mount namespaces. Unmounting it here prevents us from re-creating it
in the right way, so leave it alone.

Bug: 134706060
Test: verify mount is still there after vold starts
Change-Id: Iaac91953cbb9abfef0aaac60f74b99b16c943f87
1 file changed