Don't re-evaluate ALTQ kernel configuration due to events on non-ALTQ interfaces

Re-evaluating the ALTQ kernel configuration can be expensive,
particularly when there are a large number (hundreds or thousands) of
queues, and is wholly unnecessary in response to events on interfaces
that do not support ALTQ as such interfaces cannot be part of an ALTQ
configuration.

Reviewed by: kp
MFC after: 1 week
Sponsored by: RG Nets
Differential Revision: https://reviews.freebsd.org/D18918