nvmecontrol devlist: Handle disconnected Fabrics hosts

If a Fabrics host is disconnected, use the cached controller data
instead of reading the cdata via a pass-through command. In addition,
annotate disconnected hosts including the amount of time since the
connection was lost.

Reviewed by: chuck
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D48220