Improving Docker based Installation (#1194)

To be able to use 'vagrant ssh' from within the docker container, it is 
necessary to run within the host network context.

Include a helper alias suggestion and a note about a current issue in 
passing arguments to vagrant options which impacts the 'vagrant ssh -c 
...' syntax with an alternative.

Dockerfile

@@ -66,6 +66,8 @@ RUN for dir in boxes data tmp; \
 
 FROM base as final
 
+ENV VAGRANT_DEFAULT_PROVIDER=libvirt
+
 COPY --from=build /vagrant /vagrant
 COPY entrypoint.sh /usr/local/bin/