Web interface does not always bind to localhost by default

The webrpc interface binds to `127.0.0.1:6430` but the gui interface has chosen `192.168.0.4:6420`. Appears to happen on the orangepi in the skywire miner.

```
root@orangepiprime:~/go/src/github.com/skycoin/skycoin# make run
go run cmd/skycoin/skycoin.go --gui-dir="./src/gui/static"
abs path: /root/go/src/github.com/skycoin/skycoin/src/gui/static
runtime.Caller= /root/go/src/github.com/skycoin/skycoin/cmd/skycoin/skycoin.go
Filepath Directory= src/gui
Filepath Absolute Directory= /root/go/src/github.com/skycoin/skycoin/src/gui/static
Working Directory= /tmp/go-build956900755/b001/exe
Runtime Filename= /root/go/src/github.com/skycoin/skycoin/cmd/skycoin/skycoin.go
Runtime Directory= /root/go/src/github.com/skycoin/skycoin/cmd/skycoin
ResolveResourceDirectory: static resource dir= /root/go/src/github.com/skycoin/skycoin/src/gui/static
2018/03/19 17:23:16 Full address: http://192.168.0.4:6420
[skycoin.main:INFO] Opening database /root/.skycoin/data.db
[skycoin.visor:DEBUG] Creating new visor
[skycoin.visor:INFO] Loading blockchain
[skycoin.wallet:INFO] Loaded wallet from /root/.skycoin/wallets/2018_03_16_039e.wlt
[skycoin.gui:INFO] Web resources directory: /root/go/src/github.com/skycoin/skycoin/src/gui/static/dist
[skycoin.gui:WARNING] HTTPS not in use!
[skycoin.webrpc:INFO] Start webrpc on http://127.0.0.1:6430
[skycoin.visor:INFO] Removed 0 invalid txns from pool
[skycoin.visor:INFO] Blockchain parser start
[skycoin.daemon:INFO] Connect to trusted peers
[skycoin.gui:INFO] Starting web interface on 192.168.0.4:6420
[skycoin.pex:INFO] Pex.Run started
[skycoin.daemon:INFO] daemon.Pool listening on port 6000
[skycoin.gnet:INFO] Listening for connections on :6000...
[skycoin.daemon:DEBUG] Trying to connect to 120.77.69.188:6000
[skycoin.daemon:DEBUG] Trying to connect to 104.237.142.206:6000
[skycoin.daemon:DEBUG] Trying to connect to 47.88.33.156:6000
[skycoin.daemon:DEBUG] Trying to connect to 121.41.103.148:6000
[skycoin.daemon:DEBUG] Trying to connect to 176.58.126.224:6000
[skycoin.daemon:DEBUG] Trying to connect to 139.162.7.132:6000
[skycoin.gnet:DEBUG] Making TCP Connection to 120.77.69.188:6000
[skycoin.daemon:DEBUG] Trying to connect to 118.178.135.93:6000
[skycoin.daemon:DEBUG] Trying to connect to 172.104.85.6:6000
[skycoin.gnet:DEBUG] Making TCP Connection to 139.162.7.132:6000
[skycoin.gnet:DEBUG] Making TCP Connection to 104.237.142.206:6000
[skycoin.gnet:DEBUG] Making TCP Connection to 172.104.85.6:6000
[skycoin.gnet:DEBUG] Making TCP Connection to 47.88.33.156:6000
[skycoin.gnet:DEBUG] Making TCP Connection to 118.178.135.93:6000
[skycoin.gnet:DEBUG] Making TCP Connection to 176.58.126.224:6000
[skycoin.gnet:DEBUG] Making TCP Connection to 121.41.103.148:6000
[skycoin.main:INFO] Launching System Browser with http://192.168.0.4:6420
[skycoin.main:ERROR] Tried to open "http://192.168.0.4:6420" on default webbrowser, no screen found.
```