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