Comment 4 for bug 1613815

I'm having what appears to be this same issue:
root@mcnode2:~# lxd --version
2.0.9

root@mcnode2:/var/lib/lxd# service lxd status
● lxd.service - LXD - main daemon
   Loaded: loaded (/lib/systemd/system/lxd.service; indirect; vendor preset: enabled)
   Active: inactive (dead)
     Docs: man:lxd(1)

oot@mcnode2:~# systemctl status lxd-bridge.service
● lxd-bridge.service - LXD - network bridge
   Loaded: loaded (/lib/systemd/system/lxd-bridge.service; static; vendor preset: enabled)
   Active: failed (Result: exit-code) since Mon 2017-03-27 14:33:33 PDT; 16s ago
     Docs: man:lxd(1)
  Process: 7567 ExecStart=/usr/lib/lxd/lxd-bridge.start (code=exited, status=2)
 Main PID: 7567 (code=exited, status=2)

Mar 27 14:33:33 mcnode2 systemd[1]: Starting LXD - network bridge...
Mar 27 14:33:33 mcnode2 lxd-bridge.start[7567]: dnsmasq: failed to create listening socket for 10.50.146.1: Address already in use
Mar 27 14:33:33 mcnode2 lxd-bridge.start[7567]: Failed to setup lxd-bridge.
Mar 27 14:33:33 mcnode2 systemd[1]: lxd-bridge.service: Main process exited, code=exited, status=2/INVALIDARGUMENT
Mar 27 14:33:33 mcnode2 systemd[1]: Failed to start LXD - network bridge.
Mar 27 14:33:33 mcnode2 systemd[1]: lxd-bridge.service: Unit entered failed state.
Mar 27 14:33:33 mcnode2 systemd[1]: lxd-bridge.service: Failed with result 'exit-code'.

root@mcnode2:~# /usr/lib/lxd/lxd-bridge.start
dnsmasq: failed to create listening socket for 10.50.146.1: Address already in use
Failed to setup lxd-bridge.

root@mcnode2:~# cat /usr/lib/lxd/lxd-bridge | grep 53
    iptables "${use_iptables_lock}" -I INPUT -i "${LXD_BRIDGE}" -p udp --dport 53 -j ACCEPT -m comment --comment "managed by lxd-bridge"
    iptables "${use_iptables_lock}" -I INPUT -i "${LXD_BRIDGE}" -p tcp --dport 53 -j ACCEPT -m comment --comment "managed by lxd-bridge"
...