[DEBUG?] add configurable bridge-ip field in switchmode

The bridge itself does not reply on ARP request that the host
machine of IPOP running cannot receive packet even though it can
send packet to any IPOP and IPOP associated instance. This solution
or work around is IPOP controller provides ARP reply message to
remote peers.
Merge pull request #21 from kyuhojeong/bridge-ip-hardcode

Linux bridge not respond to ARP request
a bug fix