racktables - use apache::conf instead of file{}

..to setup the namevirtualhost config file

apache::conf is the new way as pointed out by Ori
on https://gerrit.wikimedia.org/r/#/c/147307/2/manifests/role/racktables.pp

Change-Id: I8be43bd11b2378cbcdb451525c8a4cd7f5a6c132
Merge "racktables - use apache::conf instead of file{}" into production