Unable to use 'eu-west-2' for s3 cache bucket

Summary

It looks like it is not possible to use the new London region 'eu-west-2' for gitlab-runner cache.

Steps to reproduce

Use a configuration like this one:

concurrent = 2
check_interval = 0

[[runners]]
  name = "XXXXX"
  url = "https://gitlab.com/"
  token = "XXXX"
  executor = "docker"
  [runners.docker]
    tls_verify = false
    image = "alpine:latest"
    privileged = false
    disable_cache = false
    volumes = ["/cache"]
    pull_policy = "if-not-present"
    shm_size = 0
  [runners.cache]
    Type = "s3"
    ServerAddress = "s3.amazonaws.com"
    AccessKey = "XXXX"
    SecretKey = "XXXX"
    BucketName = "XXXX"
    BucketLocation = "eu-west-2"
    Shared = true

With a s3 bucket created in 'London (eu-west-2).

Actual behavior

We get FATAL: Received: 403 Forbidden on cache extraction. No cache is uploaded on our bucket.

Expected behavior

No errors and cache should be present in s3.

Relevant logs and/or screenshots

I gathered some infos of what might be the cause for this error: Could be linked to this error https://gitlab.com/gitlab-org/omnibus-gitlab/issues/2801

In the code the new region is missing https://gitlab.com/gitlab-org/gitlab-runner/blob/60c24dadcc5046a216d790bf2346089b85ca12a2/vendor/github.com/minio/minio-go/s3-endpoints.go

Environment description

I use runners installed on some macOS.

$ docker info
Containers: 47
 Running: 5
 Paused: 0
 Stopped: 42
Images: 72
Server Version: 17.06.2-ce
Storage Driver: overlay2
 Backing Filesystem: extfs
 Supports d_type: true
 Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: bridge host ipvlan macvlan null overlay
 Log: awslogs fluentd gcplogs gelf journald json-file logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 6e23458c129b551d5c9871e5174f6b1b7f6d1170
runc version: 810190ceaa507aa2727d7ae6f4790c76ec150bd2
init version: 949e6fa
Security Options:
 seccomp
  Profile: default
Kernel Version: 4.9.41-moby
Operating System: Alpine Linux v3.5
OSType: linux
Architecture: x86_64
CPUs: 2
Total Memory: 1.952GiB
Name: moby
ID: MPMY:RRWU:YXC5:J4LL:D52A:7S7R:L72W:ASIJ:YABX:X2ZQ:26AE:WXYG
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): true
 File Descriptors: 69
 Goroutines: 104
 System Time: 2017-10-03T09:42:35.355209407Z
 EventsListeners: 2
No Proxy: *.local, 169.254/16
Registry: https://index.docker.io/v1/
Experimental: true
Insecure Registries:
 127.0.0.0/8
Live Restore Enabled: false

Used GitLab Runner version

gitlab-runner --version                                                                                                                                                                                                                                                                                                                                [11:42:35]
Version:      10.0.0~beta.55.g2055cfdc
Git revision: 2055cfdc
Git branch:   10-0-stable
GO version:   go1.8.3
Built:        Fri, 22 Sep 2017 12:22:16 +0000
OS/Arch:      darwin/amd64

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