drum: fix broken app start
drum: fix broken app start

If we find an agent that has already been launched then we continue
iterating through the list of apps instead of stopping

Fixes: #2858

jfranklin9000/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,urbit/urbit,jfranklin9000/urbit,jfranklin9000/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit,jfranklin9000/urbit,ngzax/urbit,jfranklin9000/urbit,jfranklin9000/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,urbit/urbit,ngzax/urbit