zfsd: replace vdevs with the AUX faulted state

Without this patch, vdevs faulted via AUX state would not be replaced
once the appropriate drive is replaced. ZFS does not internally use
that state, but a drive can be manually forced into such a state with a
command like zinject.

Submitted by: Goran Mekić <meka@tilda.center>
Sponsored by: ConnectWise
Differential Revision: https://reviews.freebsd.org/D46866

(cherry picked from commit 618ae939b7f95a197a0518cbb390a572bb90c6d0)