COA2-865: remove unused ca

[Yornik]

I removed the certificates that we don't use right now but added the CA for me-central-1
Original ones:
https://truststore.pki.rds.amazonaws.com/af-south-1/af-south-1-bundle.pem
https://truststore.pki.rds.amazonaws.com/me-south-1/me-south-1-bundle.pem
https://www.amazontrust.com/repository/AmazonRootCA1.pem
New one:
https://truststore.pki.rds.amazonaws.com/me-central-1/me-central-1-bundle.pem

Also, cherry-picked @pappachino commits to fix the integration test.

[djvdorp]

I can confirm that this change is the minimum required change to add the me-central-1 region which means literally include the content from the following file: https://truststore.pki.rds.amazonaws.com/me-central-1/me-central-1-bundle.pem

This can be confirmed by hand, but since we have had a point in time where there were many (most likely all available ones) were added and then subsequently removed, the diff is hard to read, so I decided to compare this PR against the state before the former PR instead (#668) to have the smallest diff possible. That would be be revision 183f4e5af7f47f47367fcc45a3cc8746aa69137f which is the last change on file etc/amazon-rds-ca.pem before 35e30369c59c13a2f888d716709bee0f21bf80c9 (which is in #668).

The diff matches the content of the AWS-supplied file exactly, so that is confirmed watertight, and can be verified via:

$ git diff 183f4e5af7f47f47367fcc45a3cc8746aa69137f..7395996bc5c9da79b94756a3b97b27fc6777ae4e etc/amazon-rds-ca.pem