*: upgrade to Go 1.10

[gyuho]

Pushed Go 1.10 test image to https://console.cloud.google.com/gcr/images/etcd-development/GLOBAL/etcd-test.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@b03fd4c). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #9334   +/-   ##
=========================================
  Coverage          ?   72.65%           
=========================================
  Files             ?      361           
  Lines             ?    30589           
  Branches          ?        0           
=========================================
  Hits              ?    22225           
  Misses            ?     6744           
  Partials          ?     1620

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[xiang90]

lgtm