Disable lxc-net on CentOS

The CentOS gate jobs have been plagued by intermittent network
connectivity issues, including failures downloading yum metadata
and failures resolving DNS records. This is happening because
dnsmasq is inaccessible and network paths are broken.

The lxc-net service is trampling on the ifup hooks that run
lxc-system-manage, which takes care of the routes, iptables rules,
and dnsmasq. This patch disables, stops, and masks the lxc-net
service on CentOS to match Ubuntu.

Closes-Bug: 1715248
Change-Id: I4cd10902e367528f59e58b4cb790131d7fbfb7b5

tasks/lxc_net.yml

@@ -47,15 +47,16 @@
     - lxc-bridge
     - lxc-interfaces
 
-# All Debian installations of LXC use the lxc-net service. This service breaks our network
-#  model and needs to be disabled
+# NOTE(mhayden): There are ifup hooks that handle the customized LXC container
+# networking. Starting lxc-net will trample over these hooks and cause
+# networking issues for containers.
 - name: Disable and stop lxc-net
   service:
     name: lxc-net
     enabled: no
     state: stopped
   when:
-    - ansible_os_family == "Debian"
+    - ansible_os_family in ["Debian", "RedHat"]
   tags:
     - lxc-net
 
@@ -66,25 +67,11 @@
     state: link
   when:
     - ansible_service_mgr == 'systemd'
-    - ansible_os_family == "Debian"
+    - ansible_os_family in ["Debian", "RedHat"]
   tags:
     - lxc-files
     - lxc-net
 
-# CentOS systems need the lxc-net service for LXC containers to boot with a
-# network interface.
-- name: Enable the lxc-net service upon reboot (CentOS)
-  service:
-    name: lxc-net
-    enabled: yes
-    state: started
-  retries: 5
-  delay: 2
-  when:
-    - ansible_os_family == 'RedHat'
-  tags:
-    - lxc-net
-
 # All Debian based systems use the interfaces.d directory for extra network configs
 #  this check ensures the needed source line is in the base config file
 - name: Ensure networking includes interfaces.d