Drop a connection, if the NOOP to keep a connection open fails due to
broken connections.
Note that I believe this function is not working as intended. We grab
one random connection and send a NOOP. This is not enough to keep all
connections open, and if we invoke this function multiple times, we
might well always get the same connection to send a NOOP through.
Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>