init_kill_services_test: wait 120s for apexd

This is likely waiting for the Java garbage collector to run,
and due to the lockless implementation of BinderProxyNativeData
and BpBinder, it's very difficult to efficiently force this
object to be deleted.

Change-Id: I4df667b9b47327967a43d75664fb506b8704f905
Fixes: 285458033
Test: N/A