servicemanager: guaranteeClient on wait register

When clients exit quickly, a client callback may not be registered yet.
We should still keep guaranteeClient set, so that they will get the
notification.

Fixes: 285202885
Test: boot
Test: aidl_lazy_test
Test: libbinder_ndk_unit_test
Change-Id: If50112a3b6c191afdadf7441638cc117fa1620ea