Fix unlinking of /dev/shm files.

Fix unlinking of /dev/shm files.

- api-segment prefix not used when unlinking shm files
- unlink root region on exit if no clients referenced
- stale reference to freed segment name
- don't add fake client to /db unless CLIB_DEBUG > 2
- turn off the gmond plugin
- clean up unused vars in vpp/api

Change-Id: I66451fcfd6ee64a12466c2d6c209050e3cdb74b7
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>
Signed-off-by: Dave Barach <dave@barachs.net>