On a fairly recent MacBook Pro laptop and on the Travis CI, the connected component check interval test takes very long time to finish.

• with -Dspark.version=1.6.3 -Dscala.version=2.10.6
  • checkpoint interval (9 minutes, 53 seconds)
• with -Dspark.version=2.1.1 -Dscala.version=2.10.6
  • checkpoint interval (3 minutes, 12 seconds)

These has caused CI to time-out for certain build variants.
We should investigate this issue.