In order to avoid the neutron-dhcp-agent container from
failing, you need to change 'MountFlags' to 'shared' in
/var/lib/systemd/system/docker.serivce. Add a precheck
so that this issue will not happen as often.
Closes-bug: #1546681
Change-Id: I339b5e93e870534fe16c6610f299ca789e5ada62