So that we can keep one python base image for our python things,
base jinja-init and gitea-init on python-base. Also, tie jinja-init
to python-base in the dependency graph and gitea-init to jinja-init.
This way if python-base updates, we'll rebuild our python images.
Update FROM lines to use full paths to images.
Change-Id: I554bf07fa8e458e443729cf4b8f40d7ceeaafa04