Fix delete_network_postcommit KeyError

Genericswitch driver was failing downstream on delete_network_postcommit
with a keyerror for network_type, however testing shows that being more
defensive here leads to success in those situations.

Co-authored-by: John Garbutt <john.garbutt@gresearch.co.uk>
Change-Id: I30b7b3d59db048e8c25917df40637383785590eb

Author: jayofdoom

networking_generic_switch/generic_switch_mech.py

@@ -79,9 +79,9 @@ def create_network_postcommit(self, context):
 
         network = context.current
         network_id = network['id']
-        provider_type = network['provider:network_type']
-        segmentation_id = network['provider:segmentation_id']
-        physnet = network['provider:physical_network']
+        provider_type = network.get('provider:network_type')
+        segmentation_id = network.get('provider:segmentation_id')
+        physnet = network.get('provider:physical_network')
 
         if provider_type == 'vlan' and segmentation_id:
             # Create vlan on all switches from this driver
@@ -164,9 +164,9 @@ def delete_network_postcommit(self, context):
         deleted.
         """
         network = context.current
-        provider_type = network['provider:network_type']
-        segmentation_id = network['provider:segmentation_id']
-        physnet = network['provider:physical_network']
+        provider_type = network.get('provider:network_type')
+        segmentation_id = network.get('provider:segmentation_id')
+        physnet = network.get('provider:physical_network')
 
         if provider_type == 'vlan' and segmentation_id:
             # Delete vlan on all switches from this driver

releasenotes/notes/delete_network_postcommit-more-defensive-19929702ba7f19fb.yaml

@@ -0,0 +1,4 @@
+fixes:
+  - |
+    Instead of always assuming we have all provider network metadata, instead
+    use a getter to avoid erroring in cases where that metadata may not be needed.