find7a: Reenable mount_all

In theory we don't need this as everything is mounted, BUT:
class late_start depends on mount_all

Also the way we were doing things since the beginning of time on the find5 was a horrible hack that we never got around to fixing...

Remove unnecessary partitions from the fstab to avoid confusing
mount_all

Change-Id: I1aa0a3ad13a1d67df811a770584203cb0d39d5ff