kumy efe4824546 Fix detecting ipv4 tunnel address
The original grep expression will fails if server support also ipv6.

```
qbittorrent    | + ip addr show tun0
qbittorrent    | + grep inet
qbittorrent    | + awk { print $2 }
qbittorrent    | + local_vpn_ip=10.2.10.6
qbittorrent    | fe80::faac:xxx:xxx:xxx/64
qbittorrent    | + pia_client_id_file=/etc/transmission/pia_client_id
qbittorrent    | + transmission_settings_file=/data/transmission-home/settings.json
qbittorrent    | + port_assignment_url=https://www.privateinternetaccess.com/vpninfo/port_forward_assignment
qbittorrent    | + cat /etc/transmission/pia_client_id
qbittorrent    | + pia_client_id=6fe581ea5b6273a88ed8421b4ceed454
qbittorrent    | + [ -z 6fe581ea5b6273a88ed8421b4ceed454 ]
qbittorrent    | + curl -d user=xxx&pass=xxx&client_id=6fe581ea5b6273a88ed8421b4ceed454&local_ip=10.2.10.6
qbittorrent    | fe80::faac:xxx:xxx:xxx/64 https://www.privateinternetaccess.com/vpninfo/port_forward_assignment
qbittorrent    |   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
qbittorrent    |                                  Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
```
2016-11-03 20:18:16 +01:00
..