Comment 1 for bug 1192381

With debug, I found the funciton port_update_end() didn't be called when quantum is busy, which caused the cache didn't updated when a port created with creating a VM, so that the host file (used for dnsmasq) didn't contain the new VM's MAC & IP address.

And I made a change, in dhcp-agent, I run a period thread to modify the sync flag to True every 10 mins.
Then the cache updated every 10 mins. Any VM who didn't get the IP from DHCP-agent then could got IP in 10 mins.

My solution couldn't fix this issue graceful but improvement.