admin: XML-metadata and SSP-metadata do not match

[tvdijen]

Describe the bug
After enabling encryption, the XML-metadata would should include a certificate with encryption=true, but the SSP-metadata does not.

To Reproduce
Steps to reproduce the behavior:

1. Set 'assertion.encryption' to 'true' on the idp-hosted metadata
2. Navigate to the admin-module and show the metadata-page
3. Compare XML to SSP-metadata

Expected behavior
The SSP-metadata should not show the 'certData' key, but the 'keys' key holding both the signing and the encryption key.

Screenshots or logs
If applicable, add screenshots and/or log files to help explain your problem.

Additional context
Running the XML-metadata through the metadata-converter will give you the proper result...
Perhaps we can re-use the code behind the converter for this, instead of calculating the SSP-metadata in several places

[tvdijen]

Closing this one in favour of #1496