Restart the neutron-dhcp-agent prior to running the
dhcp-agent-list-hosting-net command.
This will ensure that (assuming everything is working), the dhcp-agent
shows the hosting-net output appropriately.
Additionally, we should retry the "ip netns ls" command until "qdhcp"
is available, this can take some time and may cause further race
conditions.
Change-Id: I585f8c0752b9145c8441a25434769155c99ac00b
Closes-Bug: #1629346
29f02c1a9e