allow different sepolicy for third party apps

Prior support forced all third party apps to be resolved against the
default stanza of the mac_permissions.xml file when assigning seinfo
labels. This meant that all third party apps, in effect, were untrusted
regardless of cert and therefore received the same selinux domain. This
also had the unfortunate side effect of forcing certain third party apps
into the wrong domains because of shared userid requests among apps. This
patch removes that restriction and instead allows all apps, regardless of
location, to be matched against the full mac_permissions.xml policy file.
This then allows all apps signed with known good certs to receive the
same selinux domains of other apps with whom they share trust.

Change-Id: I6685f69658d672af1997a84d2c3ab5e1327a3a4c
Merge "allow different sepolicy for third party apps" into android-4.4