add unit tests to task package

[adshmh]

Added unit tests to task package, as part of work on #37.
Signed-off-by: Arash Deshmeh adeshmeh@ca.ibm.com

- What I did
Added unit tests to the cli/command/task package.

- How I did it
Added unit tests and test data to the cli/command/task package.

- How to verify it

• Run the tests (make -f docker.Makefile test)
• With this PR, the output will include:

=== RUN TestTaskPrintWithQuietOption
--- PASS: TestTaskPrintWithQuietOption (0.00s)
=== RUN TestTaskPrintWithNoTruncOption
--- PASS: TestTaskPrintWithNoTruncOption (0.00s)
=== RUN TestTaskPrintWithGlobalService
--- PASS: TestTaskPrintWithGlobalService (0.00s)
=== RUN TestTaskPrintWithReplicatedService
--- PASS: TestTaskPrintWithReplicatedService (0.00s)
=== RUN TestTaskPrintWithIndentation
--- PASS: TestTaskPrintWithIndentation (0.00s)
=== RUN TestTaskPrintWithResolution
--- PASS: TestTaskPrintWithResolution (0.00s)
PASS
ok github.com/docker/cli/cli/command/task 0.025s

- Description for the changelog
Added unit tests to cli/command/task package

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

[codecov-io]

Codecov Report

Merging #273 into master will increase coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #273      +/-   ##
==========================================
+ Coverage   46.98%   47.08%   +0.09%     
==========================================
  Files         172      173       +1     
  Lines       11693    11731      +38     
==========================================
+ Hits         5494     5523      +29     
- Misses       5882     5888       +6     
- Partials      317      320       +3

[vdemeester]

LGTM 🐮

[dnephin]

LGTM