rpcbind - Fix crash

rpcbind - Fix crash

Bring in 88cb9496ec48 from the FreeBSD repo.

The Sun RPC framework uses a netbuf structure to represent the
transport specific form of a universal transport address.  The
structure is expected to be opaque to consumers.  In the current
implementation, the structure contains a pointer to a buffer
that holds the actual address.

In rpcbind(8), netbuf structures are copied directly, which would
result in two netbuf structures that reference to one shared
address buffer.  When one of the two netbuf structures is freed,
access to the other netbuf structure would result in an undefined
result that may crash the rpcbind(8) daemon.

Fix this by making a copy of the buffer that is going to be freed
instead of doing a shallow copy.

Author:	    delphij <delphij@FreeBSD.org>
Security:   FreeBSD-SA-15:24.rpcbind
Security:   CVE-2015-7236