OMS: never filter out isStatic="true" overlays

Now that the OMS knows about overlays with the isStatic="true"
attribute, stop filtering out those overlays that have both
isStatic="true" and targetPackage="android".

This makes the OMS API more consistent: IOverlayManager.getAllOverlays
and "adb exec-out cmd overlay list" now no longer hides anything from
the caller, as was already the case for "adb exec-out cmd overlay dump"
and IOverlayManager.getOverlayInfo.

Test: manual: prepare file system, check output of adb exec-out cmd overlay list
Change-Id: I5aec941f6fd1e653910e02ed459b61f30949f8f8