check_dhcp return list in case KeyboardInterrupt

The only case when check_dhcp_on_eth is able to return bool
is KeybordInterrupt exception catching in timeout.run_with_timeout

It is required to be compliant with general fuelmenu flow

Change-Id: I60d670976bf9c5bd7804277ec8b1aa9ca77ee3b4
Related-Bug: #1313354
Merge "check_dhcp return list in case KeyboardInterrupt"