Add explicit apache2 to horizon install
Add explicit apache2 to horizon install

This package is necessary for horizon to automatically be configured
to start under ubuntu 14.04

Change-Id: I2caa6e6969037f3da98c5adb3424620334bf6d32
Closes-Bug: 1290998

kairoaraujo/openstack-manuals,openstack/openstack-manuals,Akasurde/openstack-manuals,Akasurde/openstack-manuals,openstack/openstack-manuals,potsmaster/openstack-manuals,openstack/openstack-manuals,saeki-masaki/openstack-manuals,gongysh2004/openstack-manual,saeki-masaki/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,potsmaster/openstack-manuals,gongysh2004/openstack-manual,kairoaraujo/openstack-manuals