scenario003: disable sahara on ubuntu jobs

Sahara is broken in Ubuntu / Mitaka:
ConfigParser.NoSectionError: No section: 'alembic'

While Debian is fixing it and Ubuntu is synced, we need to disable
Sahara on Ubuntu so our CI keeps rolling.

Change-Id: Iea74763c25bc52fc7637d201f614f5cbea22f459

fixtures/scenario003.pp

@@ -14,6 +14,20 @@
 # limitations under the License.
 #
 
+case $::osfamily {
+  'Debian': {
+    # sahara is broken for Ubuntu Trusty and Debian
+    # ConfigParser.NoSectionError: No section: 'alembic'
+    $sahara_enabled = false
+  }
+  'RedHat': {
+    $sahara_enabled = true
+  }
+  default: {
+    fail("Unsupported osfamily (${::osfamily})")
+  }
+}
+
 include ::openstack_integration
 include ::openstack_integration::rabbitmq
 include ::openstack_integration::mysql
@@ -24,12 +38,14 @@ include ::openstack_integration::nova
 include ::openstack_integration::trove
 include ::openstack_integration::horizon
 include ::openstack_integration::heat
-include ::openstack_integration::sahara
+if $sahara_enabled {
+  include ::openstack_integration::sahara
+}
 include ::openstack_integration::provision
 
 class { '::openstack_integration::tempest':
   trove   => true,
-  sahara  => true,
+  sahara  => $sahara_enabled,
   horizon => true,
   heat    => true,
 }