Fix recovery and enable by default

Ensure the boot partition is defined in fstab so "make dist" works
again, and also define sepolicy for recovery to enable the installation
of OTA packages with selinux enforcing. The build is now enabled by
default so we can catch future breakages more easily.

Bug: 113175337
Change-Id: Ie1a3291280ea641ea33ec8e1c575bfa0d5b4be0c
Merged-In: Ie1a3291280ea641ea33ec8e1c575bfa0d5b4be0c
Signed-off-by: Alistair Strachan <astrachan@google.com>