Init and clean up printer registry independat of state.

The printer registry is created not in sync with the states or the
activity life-cycle. It might not be initialized when stop is called as
we might have a very quick

create -> start -> stop -> finish

without time for the print subsystem to initialize.

Bug: 21749058
Change-Id: I991029a7fd0ad162c1144ff03438707f16bf0b02