Revert single comments to initial state after cancelling reply

The following discussion from !24480 (merged) should be addressed:

  • @annabeldunstone started a discussion: (+2 comments)

    If you choose Cancel to exit the new dicussion note, the comment should revert back to exactly how it looked before (a comment with no Reply... textbox button)

    Right now it ends up in this state:

    Screen_Shot_2019-01-31_at_1.50.49_PM

    It should look like all the other standalone comments:

    Screen_Shot_2019-01-31_at_1.49.49_PM