Moving the Connection events to its own executorService thread.

During the neutron integration it is observed that connection events are immediately followed by OVSDB table
configuration events and causes a similar channel lock issue that we faced recently. Hence moving it in its
own thread to avoid the Channel locking issue.

Change-Id: Ibcf147e0ff107aecfcb7987956055f563a5a17a0
Signed-off-by: Madhu Venugopal <mavenugo@gmail.com>