Do not call zypper if packages are already installed
Do not call zypper if packages are already installed

This slows down things uselessly.

SUSE-Cloud/openstack-quickstart,toabctl/openstack-quickstart,wenhuizhang/openstack-quickstart,vuntz/openstack-quickstart,hayderimran7/openstack-quickstart,sayalilunkad/openstack-quickstart,sjamgade/openstack-quickstart