Sync-up bsdinstall(8)/bsdconfig(8) list of mirrors.

SVN r253543:
Update mirror list to more closely match
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/mirrors-ftp.html

SVN r253545:
Sync-up with bsdinstall(8) FTP mirrorselect changes.

SVN r253566:
Remove ftp2.tr.freebsd.org, it is out of date.

Reviewed by:	gjb