dhcp: nettools: support option 249 (Microsoft Classless Static Route)
From [1]:
The length and the data format for the Microsoft Classless Static
Route Option are exactly the same as those specified for the
Classless Static Route Option in [RFC3442]; the only difference is
that Option Code 249 should be used instead of or in addition to
Option Code 121.
Use routes from option 249 when option 121 is not present, as already done by the dhclient backend.