SCB-127 Add shared service UT.

[little-cui]

(cherry picked from commit 8df3835)

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[coveralls]

Coverage increased (+0.1%) to 72.58% when pulling 375b051 on little-cui:master into 6e6c790 on apache:master.

[codecov-io]

Codecov Report

Merging #237 into master will increase coverage by 0.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #237      +/-   ##
==========================================
+ Coverage   68.78%   68.89%   +0.11%     
==========================================
  Files          17       17              
  Lines        3559     3559              
==========================================
+ Hits         2448     2452       +4     
+ Misses        935      933       -2     
+ Partials      176      174       -2

Impacted Files	Coverage Δ
server/service/instances.go	70.9% <0%> (+0.66%)	⬆️

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