Update code to use new network counter API.
Fix some minor compile warnings while at it.

Sponsored by:	Mellanox Technologies
Suggested by:	glebius@
MFC after:	1 week


git-svn-id: svn+ssh://svn.freebsd.org/base/head@272060 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f