Improve timeout for dhcp response waiter

Dhcp checker tool is not always receives info
on dhcp servers in network
To make checking on network with 400 vlans it takes
7 min to perform
Also get_probing_info takes same time for this number of vlans

Change-Id: I03cac773030ccfd6c6f433e117ea9240d787bbbe
Closes-Bug: #1247284
Merge "Improve timeout for dhcp response waiter"