Use macro ERROUT() to make code more laconic and follow style of other
netgraph code.

Submitted by:	Dmitry Luhtionov <dmitryluhtionov gmail.com>


git-svn-id: svn+ssh://svn.freebsd.org/base/head@273910 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f