fix: Fix incorrect printed shards number

[pawelpasterz]

Fixes #1296

Test Plan

How do we know the code works?

1. Prepare config:

   gcloud:
     app: [app from test artifacts]
     test: [multiple-success test apk]
   flank:
     max-test-shards: 50
   

2. Run flank for android with --dump-shards
3. Observe Saved 15 shards to android_shards.json is being printed.

Checklist

• Unit tested

[github-actions]

Timestamp: 2020-11-04 16:41:13
Buildscan url for ubuntu-workflow run 345918546
https://gradle.com/s/ls64leweif7s2

[codecov-io]

Codecov Report

Merging #1298 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master    #1298   +/-   ##
=========================================
  Coverage     79.71%   79.71%           
  Complexity      728      728           
=========================================
  Files           235      235           
  Lines          4525     4525           
  Branches        780      780           
=========================================
  Hits           3607     3607           
  Misses          516      516           
  Partials        402      402