tests: oneliner to run make check in a container

test/container-make-check-ubuntu-14.04.sh will

* create an ubuntu:14.04 docker container
* clone the current ceph repository or git reset --hard an existing one
* run-make-check.sh in the container, using the clone

The uses cases are:

* a developer who wants to run make check and keep working while it does
* a CI that needs to isolate from side the side effects of a failed make check run

The test/container-make-check-centos-centos7.sh script does the same and can run in parallel.