Code to pass through transport_key_id when storing secret

This can happen in either a PUT or a GET request.  The
SecretStorePluginManager must return the plugin corresponding to
the transport_key_id, and must pass the transport_key as part
of the SecretDTO, so that the plugin will know the contents are
encrypted.

Implements: blueprint add-wrapping-key-to-barbican-server
Change-Id: Ieaa2bb7881cd34bcd891764945ef3c159062d4d4
Merge "Code to pass through transport_key_id when storing secret"