[cloud-aws] signer type option does not work

[dadoonet]

Reported at:

• Setting signer type to AWS4SignerType breaks repository functionality elasticsearch-cloud-aws#242
• How to enforce aws signature to v2? elasticsearch-cloud-aws#223

This option does not work for EC2 like API or S3 like API.

We need to find a way to fix it and also to test it. A simple way for manually testing could be by using Google Storage S3 compatible API: https://cloud.google.com/storage/docs/migrating?hl=en

[xuzha]

@dadoonet could we close this, is there any more work need to be done?

[dadoonet]

Sure. Next time in your commit message, add "Closes #XXXX" and Github will close it for you. :)