SCB-129 Do not defrag the backend database after compacted.

[little-cui]

Because the etcd will change to be unavailable when the defragment is in progress.

[codecov-io]

Codecov Report

Merging #233 into master will increase coverage by 0.12%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##           master     #233      +/-   ##
==========================================
+ Coverage    68.7%   68.83%   +0.12%     
==========================================
  Files          17       17              
  Lines        3560     3562       +2     
==========================================
+ Hits         2446     2452       +6     
+ Misses        937      935       -2     
+ Partials      177      175       -2

Impacted Files	Coverage Δ
server/service/instances.go	70.38% <50%> (-0.07%)	⬇️
server/service/microservices.go	73.63% <0%> (+0.78%)	⬆️
server/service/service_dependency.go	75.86% <0%> (+0.86%)	⬆️

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[coveralls]

Coverage increased (+0.1%) to 72.563% when pulling 84ede2f on little-cui:master into bbe586c on apache:master.