Requisite=A.service
After=A.service

1) B won't start unless A is running (good).
2) B is stopped when A is stopped (good).
3) However, if I kill A, service B continues to run (bad).

BindsTo=A.service
After=A.service

1) If A is not running and I start B, then A is also started
    (I want an error, I don't want A started)
2) B is stopped when A is stopped (good).
3) B is stopped when A is killed (good)