ceph-common: skip default installs on redhat if ISO needs to be used
ceph-common: skip default installs on redhat if ISO needs to be used

Because the ISO installs would happen later in the playbook.

Signed-off-by: Alfredo Deza <adeza@redhat.com>

Resolves: rhbz#1357065

jtaleric/ceph-ansible,WingkaiHo/ceph-ansible,fgal/ceph-ansible,jsaintrocc/ceph-ansible,verdurin/ceph-ansible-1,albertomurillo/ceph-ansible,verdurin/ceph-ansible-1,bengland2/ceph-ansible,jsaintrocc/ceph-ansible,font/ceph-ansible,travmi/ceph-ansible,jtaleric/ceph-ansible,travmi/ceph-ansible,WingkaiHo/ceph-ansible,albertomurillo/ceph-ansible,WingkaiHo/ceph-ansible,bengland2/ceph-ansible,guits/ceph-ansible,fgal/ceph-ansible,ceph/ceph-ansible,ceph/ceph-ansible,albertomurillo/ceph-ansible,font/ceph-ansible,guits/ceph-ansible