Fix Apache setup

Orchestra/Webui:
- The default site is now called 000-default, so replace calls to
  "a2dissite default" by "a2dissite 000-default".
- a2ensite now requires site files to end with .conf to work
Publisher:
- overwrite 000-default.conf and default-ssl.conf instead of default and
  default-ssl
Fix glusterfs volume creation

Fix the following error message with glusterfs on Trusty:
    volume create: medias_volume_0: failed: The brick
    oscied-local-machine-5:/mnt/bricks/exp0 is is being created in the
    root partition. It is recommended that you don't use the system's root
    partition for storage backend. Or use 'force' at the end of the command
    if you want to override this behavior
OrchestraHooks.py: do not delete the rabbitmq vhost /

This does not seem to have any purpose, and it breaks rabbitmq (with error
messages like {{{badmatch,{error,{no_such_vhost,<<"/">>}}}).