[s3] Pass object parameters to head_object in exists

[czosel]

When using server-side-encryption with customer-provided keys (SSE-C), the head_object call needs the SSE-C key and algorithm - otherwise the call will fail with botocore.exceptions.ClientError: An error occurred (400) when calling the HeadObject operation: Bad Request if the file already exists.

From the docs:

If you encrypt an object by using server-side encryption with customer-provided encryption keys (SSE-C) when you store the object in Amazon S3, then when you retrieve the metadata from the object, you must use the following headers to provide the encryption key for the server to be able to retrieve the object's metadata. The headers are:

• x-amz-server-side-encryption-customer-algorithm
• x-amz-server-side-encryption-customer-key
• x-amz-server-side-encryption-customer-key-MD5

Since head_object is similar to get, we're reusing the existing logic to infer and filter the needed parameters.

Thank you in advance for your feedback!