Comment ends up on unintended line.

Summary

Comment can end up on the wrong line when one user makes a comment on a file while the second user is changing the file.

Steps to Reproduce

Steps to duplicate issue:

1. Create repository with a text file in it that is more than 1 line. I duplicated with 10 lines. This session will be called the terminal session.
2. Create a branch in the terminal session and push to Bitbucket.
3. Change file by duplicating the first line of the file. There should be two identical lines at the beginning of the file.
4. Push changes to Bitbucket and create a pull request. This will be called the web session.
5. Start a comment on line 2. Do not click the comment button.
6. In the terminal session, add a third line that is identical to the first two lines. The first three lines should be identical.
7. Add some text to the beginning of the Second line.
8. Save changes. git add, commit, push change.
9. Wait for the rescope of the pull request in Bitbucket.
10. Click the Comment button in the web session.
11. Reload web session. Comment will be on second line. The third line, the intended line, will not have a comment.