Restore compatibility with BBHN 1.1.2

This patch restores compatibility with BBHN 1.1.2.  It changes the link quality metric to match BBHN's, and also pulls in a patch that BBHN has made to the OLSRD Secure plugin.  I've tested this on my Raspberry Pi, and it's now able to talk to a Bullet M2 running BBHN 1.1.2.