From Florent Drouin: clean up resources when an open fails.

From Florent Drouin: clean up resources when an open fails.

In addition, clean up the allocation and freeing of the temporary
pathname string buffer.

Also, there's no need to set "md.device" (it's only used on Linux, and
even then used only with the old SOCK_PACKET sockets, where you have to
turn promiscuous mode off explicitly rather than having it turn off
automatically when you close the socket) or "md.timeout".