Collect basic information about the neighbours of an OLSR node:
* link quality
* neighbour link quality
* number of nodes reachable behind each neighbour
* ping times of direct neighbours
OLSR is a routing protocol (layer 3).
Reset the error mode of Net::Telnet to 'return', so that we can (try to)
log out during the error handler without invoking the error handler
(doing so resulted in "Deep Recursion" warnings from perl).
Also, return 'U' for ALL appropriate items in case of error.