Make API lint warnings errors for system & testapi

They used to be listed to not have this treatment, but we are
baselining the existing warnings and making them errors instead.

Bug: 154317059
Test: m
Change-Id: I306b5a07d1b771cc0061aaac44f881f40fbe85ed
Merged-In: I306b5a07d1b771cc0061aaac44f881f40fbe85ed