Send installerUid for verification when using PackageInstaller.

PackageManagerService when used by PackageInstaller
(installStage) does not send calling installer process id.
As a result Play Store application always triggers verification
of packages that are installed.
This causes unnecessary work on the UI thread for each new
install/update.

Bug: 22014920
Change-Id: I8cc9ba7b6fcbe26ee709a5dda284e6cdd11071f1