Convert create_backup v3 plugin to v2.1 API

Changes required to have v3 plugin natively support the V2.1
API

The create_backup action is reverted back to createBackup

Partially implements blueprint v2-on-v3-api

Change-Id: Ibac7eb2644629f4b9cf0581d9859b97f263972c8
Merge "Convert create_backup v3 plugin to v2.1 API"