WIP.

Use fig build, then fig run pdns bash. If you then build pdns, this works:

pdns/regression-tests# GMYSQLHOST=$MYSQL_1_PORT_3306_TCP_ADDR GMYSQLPASSWD=$MYSQL_1_ENV_MYSQL_ROOT_PASSWORD ./start-test-stop 5300 gmysql

A couple of tests fail due to missing software.

• don't run as root
• add more linked containers (postgres)
• install more tools (including stuff that right now is not packaged)
• set up networking for recursor testing
• switch to Ansible before the Dockerfile hits 15 lines
• set GMYSQLHOST and similar vars so start-test-stop works without a lot of typing
• include a configure script for 'the works'