Pin the upstream httpd image used for Mailman apache-shib to
version 2.4.38 so that he base is debian:stretch-slim.

Refactor the Shibboleth SP logging configuration so that default
shibd.logger, native.logger, and console.logger with details appropriate
for Docker images are in the base and can be easily copied into images.
Remove shibd.logger and native.logger from the COmanage Registry and
Mailman images as a result.

Update the Mailman 3 images and service deployment scripts so
that Apache HTTP Server with the Shibboleth SP serves as the
web proxy so that the Mailman 3 UI interfaces (Postorius and
Hyperkitty) are protected with SAML.