docker-compose: Make trillian-db-seed depend on mysql
docker-compose: Make trillian-db-seed depend on mysql

gdbelvin/trillian,gdbelvin/trillian,Martin2112/trillian,google/trillian,daviddrysdale/trillian,google/trillian,RJPercival/trillian,AlCutter/trillian,RJPercival/trillian,Martin2112/trillian,AlCutter/trillian,daviddrysdale/trillian,Martin2112/trillian,gdbelvin/trillian,daviddrysdale/trillian