Add |optional_suffix| to StartIteration()

so that PackageManagerService can iterate over files with a
specific file extension like ".so".

(cherry picked from commit a4a80693d9687982461decdcf86920b3e76bb41a)

Bug: 21957428
Change-Id: I36ba3c33a8b366a65f67cb6d156067c5caca1151
3 files changed