Bug when using one branch for two pull requests

[MVrachev]

Describe the bug
There is a bug when you reuse one branch for two pull requests and they are both opened at the same time.
Here there is this a pull request from a forked repo to an original repo:

edgexfoundry/edgex-go#1281
Then the user decided to check Precaution on its forked repository and created a pull request
on his own forked repository:

both pull requests are opened at the same time and we get this error:

It's curious that in this situation Precaution is NOT installed on the original repo but only on the forked repo.

To Reproduce
Steps to reproduce the behavior:

1. Open a pull request from forked repo to an original repo
2. Open another pull request from the forked repo to itself
3. You will get on the second pull request the error showed above

Expected behavior
We expect that Precaution will work on both instances.