Only shut down gsid when it has no more consumers.

Consumers of gsiservice must now use IGsid for its top-level interface.
IGsiService can be acquired through IGsid::getClient. When the last
reference to IGsiService is dropped, gsid will cleanly exit. Callers
should no longer stop gsid through init.

Bug: 133528572
Test: gsid cleanly exits after gsi_tool runs
Change-Id: Ie5cb80fa63e61b143f9f27cca96999a5c71dab2c
7 files changed