Remove workaround for masked redis-server.service

This is revert of 74022b48ddb6312bcc3b82a92b9bc45fdcbf04f1 and its
follow up commit 46b503f7b02f9aabad953776c2d8b4eb02859dda. The logic
was added for Debian but we no longer have Debian jobs.

Change-Id: I7633fbfbf3424f093dac5811e9c2fb8dcdf3167b

manifests/redis.pp

@@ -23,15 +23,6 @@ class openstack_integration::redis {
     }
   }
 
-  # due to issues in OpenStack CI with the redis package, we need to disable
-  # the service enable flag. The service still starts but the management of
-  # the service with systemd errors.
-  if ($::operatingsystem == 'Debian') {
-    $service_enable = false
-  } else {
-    $service_enable = true
-  }
-
   # NOTE(tobias-urdin): Manually manage redis until arioch/puppet-redis support
   # redis 4.x since that is used by Ubuntu Bionic.
   package { 'redis':
@@ -51,7 +42,7 @@ class openstack_integration::redis {
   service { 'redis':
     ensure  => 'running',
     name    => $redis_service_name,
-    enable  => $service_enable,
+    enable  => true,
     require => File_line['redis_config'],
   }
 }