[Differential] [Updated] D5853: dhclient: Log a warning instead of bailing upon "illegal" options

[sepherosa_gmail.com (Sepherosa Ziehau)]

sepherosa_gmail.com added a reviewer: freebsd-net-list.

REVISION DETAIL
  https://reviews.freebsd.org/D5853

EMAIL PREFERENCES
  https://reviews.freebsd.org/settings/panel/emailpreferences/

To: sepherosa_gmail.com, network, secteam, delphij, glebius, adrian, honzhan_microsoft.com, howard0su_gmail.com, decui_microsoft.com, freebsd-net-list