netlink: fix interface dump.

The current code missed interface addition when reallocating
temporary buffer.
Tweak the code to perform the reallocation first and add
interface afterwards unconditionally.

Reported by: Marek Zarychta <zarychtam@plan-b.pwste.edu.pl>
MFC after: 3 days

(cherry picked from commit 86fd0bdba540132ae298457e160b651f61d1db6b)