Greenkeeper continue to add comments about tests passing to closed issues

[pvdlg]

See pvdlg/karma-rollup-preprocessor#127 (comment)

The rollup dependency was updated and the issue was closed on October 17.
Even though, for each release of rollup, Greenkeeper:

• Create a branch to test the new in range rollup version => this is expected
• Adds a comment to the issue indicating the test are now passing => this is not expected
• Does not delete the branch (I had to delete them manually) => this is not expected

As a result emails notifications are sent, even though everything works as expected and many branches are created and not deleted in the repo which forces cleaning them up manually.