Fixes Facts string comparisons in CentOS 7

- CentOS Project has adopted a new rule for versioning numbers. The major number
  matches the RHEL major number, but the minor number is generated from the
  release date. For example, CentOS 7.1407.
- Adds Support for Scientific Linux.

Change-Id: I8ffb63ba3409c7595a0f13b5ec93c87b1d534d02
Closes-Bug: 1338777
Signed-off-by: Gael Chamoulaud <gchamoul@redhat.com>

manifests/params.pp

@@ -44,8 +44,8 @@ class nova::params {
         'Fedora', 'RedHat': {
           $special_service_provider = undef
         }
-        'RedHat': {
-          if ($::operatingsystemrelease < 7) {
+        'RedHat', 'CentOS', 'Scientific': {
+          if ($::operatingsystemmajrelease < 7) {
             $special_service_provider = 'init'
           } else {
             $special_service_provider = undef