Remove encoded url from end-point

[jonasfj]

Some clients can't handle urls encoded in other urls..
And we have support a lot of clients that are less than perfect...

We should refactor cloud-mirror so that:
https://cloud-mirror.taskcluster.net/v1/redirect/s3/us-east-1/<key>
mirrors <key> in a bucket hardcoded in configuration.

This will also remove the need for regular expressions, I think it's fine to make cloud-mirror less generic, we only want to use to mirror S3 buckets anyways.

Rather than passing a complete URL to cloud-mirror.

[jonasfj]

Or we could change to be something like:

• https://cloud-mirror.taskcluster.net/v1/redirect/<proto>/<hostname>/<path>

so that we don't need the extra url escaping that causes problems for some clients...

[glandium]

Or without the proto, with a hardcoded association between hostnames and protocols.