7590 sendmsg on AF_UNIX socket fails after process drops privileges
We should not assume we can call so_ux_addr_xlate() in sendmsg,

because we may no longer have the privileges needed to lookup

the AF_UNIX name again.  The problem here was with "connected"

datagram sockets, where we already know the peer address in

the internal form needed for sending.  Just use it.

The test program attached to the issue.

Added some tests for this to $SRC/tests.

Ran this on a system using AF_UNIX stuff (X11)
This build clean, and tests work fine.

I'd like to RTI it.  Can I get some "ship it"s?