apycot #1876193 apycot doesn't handle branches with more than one head [validation pending]

If a branch has more than one head, the start_period_tests looping task will try to start one test for each head, but only the tipmost one will be tested. Thus the next run of the looping task will see that some of the heads haven't been tested yet, and restart the test on that branch every time.

prioritynormal
typebug
done in2.1.0
load left0.000
closed by#003e68913c7f Only consider the tipmost head of a branch for testing (closes #1876193)