assorted cleanups: use Println, rename vars for consistency

[thaJeztah]

minor cleanups: use Println, rename vars for consistency

• use Println to print newline instead of custom format
• use apiClient instead of client for the API client to prevent shadowing imports.
• use dockerCLI with Go's standard camelCase casing.
• suppress some errors to make my IDE and linters happier

cli/command/volume: remove example and var for long description

This was the only command for which we set the "example" field; while
we could consider doing this for other commands, we need to look what's
best w.r.t. duplicating the information maintained in markdown.

Also remove the intermediate variable used for the long description,
as this was also the only location where we used one.

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 51.67785% with 144 lines in your changes missing coverage. Please review.

Project coverage is 59.42%. Comparing base (4d7fe01) to head (987da09).
Report is 64 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5783      +/-   ##
==========================================
- Coverage   59.42%   59.42%   -0.01%     
==========================================
  Files         347      347              
  Lines       29402    29398       -4     
==========================================
- Hits        17472    17469       -3     
+ Misses      10958    10957       -1     
  Partials      972      972              

[thaJeztah]

Derp; missed a newline change somewhere;

=== FAIL: e2e/cli-plugins TestCliInitialized/withhook (0.03s)
    run_test.go:227: assertion failed: 
        --- ←
        +++ →
        @@ -1,2 +1 @@
        -Plugin·PersistentPreRunE·called
        -
        +Plugin·PersistentPreRunE·called
```

We should also look at the cli-docs tool to ignore leading/trailing whitespace in these, so that we can use a more ergonomic way of setting these for multiple lines. I _think_ Cobra itself trims leading/trailing whitespace;

```patch
diff --git a/docs/reference/commandline/cp.md b/docs/reference/commandline/cp.md
index ded96d6..0ca9e7c 100644
--- a/docs/reference/commandline/cp.md
+++ b/docs/reference/commandline/cp.md
@@ -8,6 +8,7 @@ and extract it to a directory destination in a container.
 Use '-' as the destination to stream a tar archive of a
 container source to stdout.
 
+
 ### Aliases
 
 `docker container cp`, `docker cp`
```

spam account

[thaJeztah]

Oh! Needs a rebase; conflict in one file; let me do so