routesock.c:k_req_incoming() - Retry read() of routing socket on EAGAIN

Reading the routing table sometimes takes a while on FreeBSD.  This
commit allows for retrying three times before giving up.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
Cleanup and improve debug output

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>