can't bridge an I/F with jumbo to taps, deleted bridge 'flags' are sticky if you remake them

I just found a couple of odd quirks in bridge

1) you can't bridge an MTU 9000 interface to taps. If you dial it back
to 1500 it works fine. I might have missed this being a limit in the
man

2) when you delete a bridge, and re-create it, some of the addm
"history" can come live. faulty debug suggests some state in the
kernel/network space isn't wiped clean. Maybe this is a good thing,
the most likely outcome is you wanted much the same but.... POLA

FreeBSD 12-2-RELEASE-p6 (if this is fixed in newer FreeBSD)

-G