Remove hardcoded list of AGENT_PLUGIN_PYTHON_VERSIONS in run_tests.sh

... and grep the value from the defines.make instead of using make to
print the value to come closer to the target of make free builds.

Community edition is already a free build, but that is not what is ment

CMK-37829

Change-Id: I8a9b9fdc6eee9dde183b7853393ac1c50029cdbd