HTTPError 409: Operation failed because another operation was already in progress
Cloud SQL instances are constantly being monitored so issues like this one should be resolved within a few hours. However, if your Cloud SQL instance is still stuck:
File a support ticket if you have or are able to get a Google Cloud Platform Support package (this would be the fastest way to get this issue resolved).
If you do not have a support package, try opening a private Issue Tracker describing the problem, remembering to include all the relevant details such as project ID and instance name.