drbd: Replace conn_get_by_name() with drbd_find_resource()

So far, connections and resources always come in pairs, but in the future with
multiple connections per resource, the names will stick with the resources.

Signed-off-by: Andreas Gruenbacher <agruen@linbit.com>
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>

diff --cc drivers/block/drbd/drbd_int.h
Simple merge

diff --cc drivers/block/drbd/drbd_main.c
Simple merge

diff --cc drivers/block/drbd/drbd_nl.c
Simple merge