altq_add() and its descendants. Currently altq(4) in FreeBSD is configured
via pf(4) ioctls, which can't configure altq(4) w/o holding locks.
Fortunately, altq(4) code in spife of using M_WAITOK is ready to receive
NULL from malloc(9), so change is mostly mechanical. While here, utilize
M_ZERO instead of bzero().
A large redesign needed to achieve M_WAITOK usage when configuring altq(4).
Or an alternative (not pf(4)) configuration interface should be implemented.
Reported by: pluknet