Return the actual baud rate programmed in the hardware rather than 115200.
This allows the "3wire" entry in /etc/ttys (with no speed specified) to work.
Test for absence of M_NOFREE before attempting to purge the mbuf's tags.
This will leave more state intact should the assertion go off.

MFC after:	1 month
Add ObsoleteFiles.inc OLD_FILES entries for libnv

X-MFC with: r271241
Submitted by: pjd
Pointyhat to: ngie
Sponsored by: EMC / Isilon Storage Division