netgraph/ng_bridge: Handle send errors during loop processing

[donner]

Summary

If sending out a packet fails during the loop over all links, the
allocated memory is leaked and not all links receive a copy. This
patch fixes those problems, clarifies a premature abort of the loop,
and fixes a minory style(9) bug.

PR: 255430
MFC: 1 week
Submitted by: Dancho Penev

Test Plan

Build a bridge over a bunch of ng_eiface(4). Set one of the
interfaces down (causing the error), try to send out a broadcast
packet and monitor all the interfaces.

[donner]

• Free packet if not send at all.

[julian]

sys/netgraph/ng_bridge.c

643

I would do: if error ( error stuff; return error} followed by the non error case continuing on with one level less indent. just a style thing.. result is the same

[donner]

• Restructure the error handling in a more common way.