Modify the script so that it can be used by the *aaS functional tests.
This is done by allowing callers, namely other *aaS repos, to override
information, like the project name and virtual environment used (for
example, VPNaaS has two functional jobs with different virtual env).
Change-Id: I450273036e938a4acc9a7bc1dc193a9c207b2d58
Closes-Bug: #1446807