Fix alignment of client built time in version output

[leanderjanssen]

- What I did
Add one more tab to the Built time to align the output of the docker client version.

- How to verify it

Before:

$ docker version
Client:
 Version:	18.01.0-dev
 API version:	1.35
 Go version:	go1.9.2
 Git commit:	c97c6d6
 Built:	Wed Dec 27 20:11:19 2017
 OS/Arch:	linux/amd64
 Experimental:	false

After:

$ docker version
Client:
 Version:	18.01.0-dev
 API version:	1.35
 Go version:	go1.9.2
 Git commit:	0dd05ac1
 Built:		Thu Dec 28 09:19:35 2017
 OS/Arch:	linux/amd64
 Experimental:	false

- Description for the changelog

Fix alignment of client built time in version output

Signed-off-by: Leander Janssen leander@slaco.net

[codecov-io]

Codecov Report

Merging #769 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #769   +/-   ##
=======================================
  Coverage   53.46%   53.46%           
=======================================
  Files         218      218           
  Lines       14642    14642           
=======================================
  Hits         7829     7829           
  Misses       6327     6327           
  Partials      486      486

[thaJeztah]

Ah! I think the alignment was due to a bug in the tabwriter, and this would not be the correct fix

ping @tiborvass PTAL

[leanderjanssen]

In GitHub this looks a bit weird, but in the actual code a single tab character is used.
Because the word Built is so short compared with the rest, two tabs are required to align it correctly.

[thaJeztah]

The tabwriter is meant to convert the tabs to spaces during presentation, so that the columns are always aligned properly. There was a bug in the tabwriter though, that caused the alignment to not work properly, so it was temporarily disabled (IIRC).

I'm not exactly sure what the bug was, but @tiborvass mentioned that, so I guess he knows more. If that is resolved, alignment should work again (and this change would not be needed)

[leanderjanssen]

Ah I see, I was actually quite surprised to see hard tabs in the code.

[vdemeester]

ping @tiborvass

[tiborvass]

Ugh, sorry for delay on this, thanks @leanderjanssen, but we need to use tabwriter here and I remember having some issues with it. If you want to tackle it let me know otherwise I'll try.

[vdemeester]

LGTM 🐯
Let's go for that now and we'll see how to make it better later 👼

[thaJeztah]

opened #965, using tabwriter