Alter condition for starting RulesManagerService

Modify the condition used for starting RulesManagerService:
use mOnlyCore rather than disableNonCoreServices. mOnlyCore is
important for the secure lock screen and when mOnlyCore is true
the RulesManagerService cannot perform trust checks. Therefore,
disable the RulesManagerService when mOnlyCore == true.

disableNonCoreServices is apparently not used.

Bug: 64057583
Test: Boot device with time zone updates enabled and with a lock
      pattern set.

Change-Id: Idd7cb6e11b1a91dfe7394f6c98f8fa3e0eec9dce