docker-ce: add bip uci to default config

Signed-off-by: Florian Eckert <fe@dev.tdt.de>

utils/docker-ce/files/etc/config/dockerd

@@ -4,5 +4,8 @@ config globals 'globals'
 	option data_root "/opt/docker/"
 	option log_level "warn"
 	option hosts "unix://var/run/docker.sock"
+	# If the bip option is changed, dockerd must be restarted.
+	# A service reload is not enough.
+	option bip "172.18.01./24"
 #	list registry_mirror "https://<my-docker-mirror-host>"
 #	list registry_mirror "https://hub.docker.com"