Apply "POST/DELETE" rules to agents_client

As the consistent-service-method-names bp, "POST /resources" methods'
names should be "create_<resource name>" and "DELETE /resources/<id>"
methods' names should be "delete_<resource name>".

This patch applies the rules to agents_client.

Partially implements blueprint consistent-service-method-names

Change-Id: I505fa196c574027692497848d235781d903cb9f6
5 files changed