Revert "Revert "Merge remote-tracking branch 'origin/pr/498' into develop""

This reverts commit 2a28c737b7df764c921d5b7e248f35e44f599a90.
Fix how we handle the login secret
Since there have been two properties for this setting we have decided that
1. We deprecate uaa.login.client_secret - yet, if that is the only property available, we will use it for backwards compatibility
2. If the property uaa.clients.login.secret is present, this property will override the uaa.login.client_secret

There is no way that the two different properties can vary, and break the deployment.
This is a fix for https://github.com/cloudfoundry/cf-release/commit/dab97e88506160ad94c61f0448179c88158e08dd