System package permission decls take precedence over 3rd party apps'

In particular, if a 3rd party app tries to define a permission that
turns out to be defined by system packages following an upgrade,
the system package gets ownership and grants are re-evaluated
on that basis.

Bug 11242510

(Cherry-pick backport to JB)

Change-Id: Iabf7b6280e6c6674a51af5624142bd19ea0750ed