Add a Tunnel end-point variable for Neutron configuration

The HOST_IP address is being used as IP address
for end-point tunnel configruation. A new variable is
needed to specify a different IP address for the tunnel
end-point that Neutron will use

Change-Id: Ic7fb4853df167e78bf882af6a712b903db754dc2
Closes-bug: #1340433
Merge "Add a Tunnel end-point variable for Neutron configuration"