Don't disable DND permission settings for apps that have disabled NLS

ZenAccessController.getPackagesRequestingNotificationPolicyAccess
was including disabled packages.
We change this behavior to exclude any disabled package

Test: make -j64 RunSettingsRoboTests ROBOTEST_FILTER="com.android.settings.applications.specialaccess.zenaccess.ZenAccessControllerTest"
Change-Id: I354b8f0bdbf602d1f35233d5003ce09f01df3cb2
Fix: 141318822