CLI tools do not cache auth token

Description

CLI tools do not cache the registry auth token across invocations, even though token has expires_in field set to one hour

Steps to reproduce the issue:

1. Perform an action against a registry that requires auth tokens
2. Get 401 redirect to acquire token
3. Acquire token with 3600 second expiration, and use it to perform operation
4. Try registry operation again one second later

Describe the results you received:

CLI appears to have forgotten the auth token just obtained, and must go through the process acquiring it again.

Describe the results you expected:

After acquiring an auth token with an expires_in field, use that token until it expires.

Additional information you deem important (e.g. issue happens only occasionally):

Always happens.

Output of docker version:

Client:
 Version:         1.12.6
 API version:     1.24
 Package version: docker-1.12.6-32.git88a4867.el7.centos.x86_64
 Go version:      go1.7.4
 Git commit:      88a4867/1.12.6
 Built:           Mon Jul  3 16:02:02 2017
 OS/Arch:         linux/amd64

Server:
 Version:         1.12.6
 API version:     1.24
 Package version:
 Go version:      go1.7.6
 Git commit:      d9ad3fc
 Built:           Thu Oct 26 03:30:45 2017
 OS/Arch:         linux/amd64

Output of docker info:

Containers: 17
 Running: 17
 Paused: 0
 Stopped: 0
Images: 22
Server Version: 1.12.6
Storage Driver: overlay
 Backing Filesystem: extfs
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: overlay null bridge host
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Security Options: seccomp selinux
Kernel Version: 4.13.9-coreos
Operating System: Container Linux by CoreOS 1520.8.0 (Ladybug)
OSType: linux
Architecture: x86_64
Number of Docker Hooks: 2
CPUs: 24
Total Memory: 62.88 GiB
Name: core01.tec1.tivo.com
ID: MXJB:SJWY:3OZ5:3JY6:6G7N:FYJX:D2HN:PBWX:3W7K:DTOV:LVGV:MLSO
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Insecure Registries:
 127.0.0.0/8
Registries:

Additional environment details (AWS, VirtualBox, physical, etc.):

running in CoreOS, with Artifactory as docker registry.

Start by tracing Docker CLI registry authentication and token handling, then reproduce the repeated registry operation against an authenticated Artifactory registry. The work is done when a token with an expires_in value is reused across invocations until it expires, without requiring another token acquisition.