Rename ci Docker file

SDL Continuous Integration (ci) tests are not anymore run on a docker
but instead directly on the Jenkins minion (virtual machine). That's
why remove unnecessary ci directory with its docker files and move the
files to docker_test directory. Docker can be used for local testing
purposes.

Change-Id: Iac527243927c925b35a03fcbaef36972bafa4488
Signed-off-by: Timo Tietavainen <timo.tietavainen@nokia.com>