drbd: Ignore the exit code of a fence-peer handler if it returns too late
In case the connection was established and lost again before
the a fence-peer handler returns, ignore the exit code of this
instance. (And use the exit code of the later started instance)
Signed-off-by: Andreas Gruenbacher <agruen@linbit.com> Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>