Update flannel to use sd-notify

Remove hacky loop to check for Docker configs, and update to use
sd-notify instead to alert systemd when flannel is ready.

Signed-off-by: Yu Qi Zhang <jerzhang@redhat.com>

Closes: #24
Approved by: giuseppe

flannel/flanneld-run.sh

@@ -7,7 +7,7 @@ echo "EnvironmentFile=-/run/$NAME/docker" >> /etc/systemd/system/docker.service.
 # Ensure this file doesn't already exist.
 rm -f run/flannel/subnet.env
 
-/usr/bin/flanneld &
+NOTIFY_SOCKET=/dev/null /usr/bin/flanneld &
 child=$!
 
 while test \! -e /run/flannel/subnet.env
@@ -17,4 +17,6 @@ done
 
 /usr/libexec/flannel/mk-docker-opts.sh -k DOCKER_NETWORK_OPTIONS -d /run/flannel/docker
 
+systemd-notify --ready
+
 wait $child

flannel/service.template

@@ -7,9 +7,10 @@ After=$AFTER
 Before=docker.service
 
 [Service]
+Type=notify
+NotifyAccess=all
 ExecStart=$EXEC_START
 ExecStop=$EXEC_STOP
-ExecStartPost=/usr/bin/sh -c "while test \! -s ${RUN_DIRECTORY}/${NAME}/docker; do sleep 0.1; done"
 ExecStopPost=/bin/rm /etc/systemd/system/docker.service.d/$NAME.conf
 Restart=on-failure
 WorkingDirectory=$DESTDIR