kea-netconf should print out control channel being opened

While reviewing !163 (merged) I've tried to start kea-netconf without dhcp4 or dhcp6 running. The error message I got was confusing. It was clear that some file is missing, but it was never said which file:

2018-12-10 19:40:24.202 INFO  [kea-netconf.netconf/29469] NETCONF_STARTED Netconf (version 1.5.0-beta2-git) started
2018-12-10 19:40:24.203 INFO  [kea-netconf.netconf/29469] NETCONF_GET_CONFIG_STARTED getting configuration from dhcp4 server
2018-12-10 19:40:24.203 ERROR [kea-netconf.netconf/29469] NETCONF_GET_CONFIG_FAILED getting configuration from dhcp4 server failed: config-get command failed with communication error: No such file or directory
2018-12-10 19:40:24.203 INFO  [kea-netconf.netconf/29469] NETCONF_GET_CONFIG_STARTED getting configuration from dhcp6 server
2018-12-10 19:40:24.203 ERROR [kea-netconf.netconf/29469] NETCONF_GET_CONFIG_FAILED getting configuration from dhcp6 server failed: config-get command failed with communication error: No such file or directory
2018-12-10 19:40:24.203 INFO  [kea-netconf.netconf/29469] NETCONF_SET_CONFIG_STARTED setting configuration to dhcp4 server
2018-12-10 19:40:24.217 DEBUG [kea-netconf.netconf/29469] NETCONF_SET_CONFIG set configuration to dhcp4 server: {
  "Dhcp4": { }
}
2018-12-10 19:40:24.217 ERROR [kea-netconf.netconf/29469] NETCONF_SET_CONFIG_FAILED setting configuration to dhcp4 server failed: config-set command failed with communication error: No such file or directory
2018-12-10 19:40:24.217 INFO  [kea-netconf.netconf/29469] NETCONF_SUBSCRIBE_CONFIG subscribing configuration changes for dhcp4 server with kea-dhcp4-server module
2018-12-10 19:40:24.229 INFO  [kea-netconf.netconf/29469] NETCONF_SET_CONFIG_STARTED setting configuration to dhcp6 server
2018-12-10 19:40:24.243 DEBUG [kea-netconf.netconf/29469] NETCONF_SET_CONFIG set configuration to dhcp6 server: {
  "Dhcp6": { }
}
2018-12-10 19:40:24.243 ERROR [kea-netconf.netconf/29469] NETCONF_SET_CONFIG_FAILED setting configuration to dhcp6 server failed: config-set command failed with communication error: No such file or directory

IMHO the netconf daemon should print out unix socket path/http URL on info level. This would be on par with what dhcp4/6 does, it prints the unix socket path when opening control channel:

COMMAND_ACCEPTOR_START Starting to accept connections via unix domain socket bound to /tmp/kea-dhcp4-ctrl.sock