(bug 44041) adapt role::cache::mobile for beta

* role::cache::mobile now includes the role::cache::configuration to
  properly load the beta configuration.
* setup the varnish filesystem on /dev/vdb
* hack the storage commandline for deployment instances
* disable varnish logging on beta, one can use varnishncsa from the
  command line to get the same results.
* tweak mount varnish::setup_filesystem() mount options for labs: it
  does not support 'logbufs=8' and needs 'comment=cloudconfig'

Change-Id: I198e5ae4cdea89af82901ddc1461ef4701e9e1cc