Add delete_agent to NetworkClientJSON

This patchset add delete_agent method that implements respective API [1]

[1] https://developer.openstack.org/api-ref/network/v2/index.html#delete-agent

Change-Id: I0f4927944cb48a19eb8cdff5312557b3ba044420
Closes-Bug: 1792007
diff --git a/releasenotes/notes/agents-client-delete-method-de1a7fb3f845999c.yaml b/releasenotes/notes/agents-client-delete-method-de1a7fb3f845999c.yaml
new file mode 100644
index 0000000..01c94f4
--- /dev/null
+++ b/releasenotes/notes/agents-client-delete-method-de1a7fb3f845999c.yaml
@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Added a new method ``delete_agent`` to the AgentsClient class that
+    implements agent deletion according to the neutron API.
+    https://developer.openstack.org/api-ref/network/v2/index.html#delete-agent
+