Fix support for OCI defined tags annotation in app.yaml #728

The oracle.com/oci/definedTags annotation is defined in YAML application file app.yaml but it's not actually supported.

Annotation definition for defined tags comes from fn_go project and it's supposed to be a map of maps of strings; therefore, annotation structure is supposed to look like this:

...
annotations:
  oracle.com/oci/definedTags:
    <namespace1>:
      <tag-name-1>: <tag-value-1>
    <namespace2>:
      <tag-name-2>: <tag-value-2>

Despite defining the required structure, fn command line tool returns the generic error 'invalid defined tags annotation'.