Adding support for canal network plugin

This patch provides support for Canal network plugin installation
as a self-hosted app, see the following link for details:

https://github.com/tigera/canal/tree/master/k8s-install

roles/network_plugin/canal/defaults/main.yml

@@ -0,0 +1,11 @@
+# The interface used by canal for host <-> host communication.
+# If left blank, then the interface is chosing using the node's
+# default route.
+canal_iface: ""
+
+# Whether or not to masquerade traffic to destinations not within
+# the pod network.
+canal_masquerade: "true"
+
+# Log-level
+canal_log_level: "info"