Merge pull request #86 from changbl/working

parallelize arp scripts to speedup
Gateway high availability

The controller installs two copies of the same flow entry
on (master gateway, backup gateway).
Merge pull request #87 from powerist/failover

Gateway high availability
Fix ARP eval scripts

(1) Timeout calculation

(2) ping.log text processing

(3) Speedup via more parallelizatoin