Revert "Allow kernel domain, not init domain, to set SELinux enforcing mode."

The build is broken. Reverting temporarily to fix breakage.

libsepol.check_assertion_helper: neverallow on line 4758 violated by allow init kernel:security { setenforce };
Error while expanding policy
make: *** [out/target/product/mako/obj/ETC/sepolicy_intermediates/sepolicy] Error 1
make: *** Waiting for unfinished jobs....


This reverts commit bf12e225.

Change-Id: I78a05756d8ce3c7d06e1d9d27e6135f4b352bb85