Locking around build_requested for race condition (AUE-382)

Lock around build requested to avoid a scenario where builds that are requested are not made.

Would especially like input from @nnutter and @tmooney
Yeah--it sounds like we shouldn't worry about `GENOME_SOFTWARE_RESULT_TEST_NAME` here.

As an aside, people who eagerly archive/purge things should be aware of this fact about test names--often things with test names are more aggressively archived/purged than normal results.