This patch splits distro variables into two:
- cinder_*_distro_packages defines dependant packages
- cinder_*_service_distro_packages defines cinder service packages itself
So that we're installing cinder_*_distro_packages both for source and distro
installs while cinder_*_service_distro_packages are only for distro ones.
Also since only qemu-tools depends on librbd, we leave it alone in
cinder_volume_distro_packages_tools.
Change-Id: I746c800dc75b39f57f7c707aedf35f6814cfdef0
75d0f298c6