sockets: Bypass "replace empty @path" for abstract unix sockets
unix_listen_saddr() replaces empty @path by unique value. It obtains
the value by creating and deleting a unique temporary file with
mkstemp(). This is racy, as the comment explains. It's also entirely
undocumented as far as I can tell. Goes back to commit
d247d25f18
"sockets: helper functions for qemu (Gerd Hoffman)", v0.10.0.
Since abstract socket addresses have no connection with filesystem
pathnames, making them up with mkstemp() seems inappropriate. Bypass
the replacement of empty @path.
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>