Fix hostname inconsistencies during script execution

When `--with-iou` and `--with-openvpn` are both enabled, hostname
were updated in `/etc/hostname` but not on the running system (only
changed after reboot). So the old hostname were used in MOTD and
client OpenVPN config URL.

scripts/remote-install.sh

@@ -185,6 +185,8 @@ then
 
     # Force the host name to gns3vm
     echo gns3vm > /etc/hostname
+    hostname gns3vm
+    HOSTNAME=$(hostname)
 
     # Force hostid for IOU
     dd if=/dev/zero bs=4 count=1 of=/etc/hostid