Fixes#550.
This will make it possible to configure the advertised adresses for
SerfLan, SerfWan and RPC. It will enable multiple consul clients on a
single host which is very useful in a container environment.
This option might override advertise_addr and advertise_addr_wan
depending on the configuration.
It will be configureable with advertise_addrs. Example:
{
"advertise_addrs": {
"serf_lan": "10.0.120.91:4424",
"serf_wan": "201.20.10.61:4423",
"rpc": "10.20.10.61:4424"
}
}