Deadlock when changing ExternalDirectories encryption key and adding/updating directory at the same time

Issue Summary

Deadlock occurs when changing the External Directories encryption key and adding/updating the external directory at the same time.

The issue makes all administrative action on external directories (adding new, updating, removing, reordering) impossible until Jira is restarted. (Affects all nodes)

The issue doesn't affect other Jira functionalities like login, viewing issues, viewing user profile, managing users, etc.

Steps to Reproduce

1. Have Jira instance with External Directories
2. Change encryption key `crowd.encryption.encryptor.default` via `Advanced Setting` in Jira
3. At the same time as Step 2 try to add a new External Directory to Jira or update existing one
4. Have bad luck

Expected Results

There is no deadlock and Jira work normally.

Actual Results

All administrative actions on external directories freeze until Jira restart.

Workaround

If deadlock already happened then the only solution is to restart the Jira node that is deadlocked.

Deadlock can be prevented by waiting few minutes after changing the encryption key before doing any changes to external directories.

Notes

Each node can be restarted one by one with zero downtime. Just make sure that nobody tries to change external directories during the restart procedure.