ci: Add more fine-grained control on tests

Allow to test only an app of a component, if the input has the following
form:

    component.app

e.g. astakos.im
ci: Handle Images with many users

Choose from the user list of an Image the first user as the admin user.
ci: Update configuration

Update the url for the Synnefo repo and add a flavor with more RAM as
default.
ci: Add coverage in packages needed for testing
ci: Add nosetests for astakosclient

Use nosetests to test astakosclient. If coverage is present in the
system, use coverage in cojunction with nosetests.

Also, fix reports generated by coverage as well as other coverage
issues.