Drop SELinux management rules from AOSP.

As AOSP does not support the device admin API or the older
SEManager system app, just drop the allow rules associated with
permitting SELinux management via device admin or a system app.

Change-Id: Icdf40c9e6d343b19c156e4c7aea4cfb8c5f234ad
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>