Remove duplicate TenantSecret on secret PUT call.

During a two step Secret creation (so a POST followed by a PUT) a duplicate TenantSecret
record is created.  This commit is to remove this duplicate record.

Change-Id: If877f6fb45de1b772bdbdeac4f757e8269cb04f3
Implements: blueprint datamodel-remove-dup-tenantsecret-on-put
Change from using 'cypher_type' to 'mode' in API and code base.

The term 'mode' is better aligned with the cypher community than
'cypher_type' is. Therefore, it would be less confusing to change
the name of this attribute prior to the M3 feature freeze.

Change-Id: Ibf99bd730e9a3ff7bd1f49f4252cc860a60e9295