Add `data` extra-binding to influence overlay traffic

Also fix handling of chassis system ID and cert req by rebuilding
charm with updated code from layer-ovn.
Ref: openstack-charmers/charm-layer-ovn#8

Change-Id: I82d20516eeeb33edd66c5100c070258a6003cfa3

src/README.md

@@ -29,7 +29,12 @@ This charm supports the use of Juju Network Spaces.
 By binding the `ovsdb` endpoint you can influence which interface will be used
 for communication with the OVN Southbound DB as well as overlay traffic.
 
-    juju deploy ovn-chassis --bind "ovsdb=data-space"
+    juju deploy ovn-chassis --bind "ovsdb=internal-space"
+
+By binding the `data` extra-binding you can influence which interface will be
+used for overlay traffic.
+
+    juju deploy ovn-chassis --bind "data=overlay-space"
 
 ## Port Configuration
 

src/metadata.yaml

@@ -10,6 +10,8 @@ series:
   - bionic
   - eoan
 subordinate: true
+extra-bindings:
+  data:
 provides:
   nova-compute:
     interface: neutron-plugin