Bump the version of the Docker client image in Circle CI

[sargun]

This is the image being used to do docker image builds

[coveralls]

Pull Request Test Coverage Report for Build 1072

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 25.915%

---

Files with Coverage Reduction	New Missed Lines	%
launchguard/client/client.go	3	72.11%

Totals
Change from base Build 962:	-0.03%
Covered Lines:	2408
Relevant Lines:	9292

---

💛 - Coveralls

[codecov]

Codecov Report

Merging #128 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #128   +/-   ##
=======================================
  Coverage   35.71%   35.71%           
=======================================
  Files          65       65           
  Lines        7353     7353           
=======================================
  Hits         2626     2626           
  Misses       4426     4426           
  Partials      301      301