build: Ensure docker containers are removed, fix Darwin
build: Ensure docker containers are removed, fix Darwin

This changes the Docker command to include --rm to clean up.

Also fixes user/group handling on Docker Toolbox, where the IDs are
1000:50 and not the current user/group.

apcera/kurma,apcera/kurma,apcera/kurma,apcera/kurma,apcera/kurma