Add Coverity Scan to CI
This job requires two CI variables set 'COVERITY_SCAN_PROJECT_NAME' and 'COVERITY_SCAN_TOKEN'. The former's value is project name (in our case most notably the branch on which this job is executed - e.g. 'bind-master'), the latter is it's token.
Coverity Scan tools are expected to be in the image.
Edited by Michal Nowak