Properly use implicit outputs

This had been defining two independent rules to run these tests. Use the
kati extension to claim that both outputs are being written by the same
execution.

Test: m RunStorageManagerRoboTests
Test: m out/target/product/generic/obj/ROBOLECTRIC/RunStorageManagerRoboTests_intermediates/test-{output,retval}.txt
Test: diff build-aosp_arm.ninja, expected changes
Change-Id: I559afa9a13172567fcda67393a08b6a2a6dde540