docs: Revised descriptions of binding and connecting to services.

docs: Revised descriptions of binding and connecting to services.

Clarified that Context.bindService() returning true only indicates
that the system has found a service to bind to the client and that
ServiceConnection.onServiceConnected() might not be called if the
service encounters an error, such as crashing during startup.

Test: make ds-docs

Bug: 63118511
Change-Id: I0906de76abf4124d74f7f4f80ac0eab3cbf94f7e