Merge pull request #928 from jjlin/healthcheck

docker/Dockerfile.j2

docker/aarch64/mysql/Dockerfile

docker/aarch64/sqlite/Dockerfile

docker/amd64/mysql/Dockerfile

docker/amd64/mysql/Dockerfile.alpine

docker/amd64/postgresql/Dockerfile

docker/amd64/postgresql/Dockerfile.alpine

docker/amd64/sqlite/Dockerfile

docker/amd64/sqlite/Dockerfile.alpine

docker/armv6/mysql/Dockerfile

docker/armv6/sqlite/Dockerfile

docker/armv7/mysql/Dockerfile

docker/armv7/sqlite/Dockerfile

docker/healthcheck.sh