Fault-tolerant live migration

The live migration, including RPC, is logged each time.
The back-up controller checks the logging and finish all
remaining tasks.
Property: Live migration eventually finishes consistently.
Merge pull request #54 from powerist/working

Fault-tolerant live migration
Fault-tolerant source learning and ARP learning
Merge pull request #55 from powerist/working

Fault-tolerant source learning and ARP learning
Use DHCP message for ARP learning
Merge pull request #56 from powerist/dhcp

Use DHCP message for ARP learning
Merge pull request #57 from changbl/working

Fix bug: log_formatter being passed in oslo.config
Add function extract_ip_addr
Merge pull request #58 from powerist/portname

Add function extract_ip_addr
Remove RPC when there is only one datacenter
Merge pull request #59 from powerist/working

Remove RPC when there is only one datacenter
Add arp_bcast in inception.conf to turn on/off ARP broadcast
Merge pull request #60 from powerist/arp

Add arp_bcast in inception.conf to turn on/off ARP broadcast
Add cleanup-zk script