Add a basic test for netd dumpsys output format.

This CL contains a test that calls the dump method on the netd
service (basically, "dumpsys netd") and checks that the logging
output for some of the IPCs is correct.

Bug: 172188290
Test: test-only change
Change-Id: Ib2d41e8cbd0e2d03fb7f62e1cb728bd594053fd7