Deleting a repository can result in a Server unreachable error

Issue Summary

Since the introduction of last change to the AnalyticsRepositoryDeletedEvent and AnalyticsRepositoryModifiedEvent some instance are returning Server unreachable error when these events are generated such as deleting or updating a repository.
 
This can be seen in the profiler logs where findByRepository takes a long time to complete

[154156.7ms] - Page com.atlassian.stash.internal.repository.RepositoryActivityDao.findByRepository(int,PageRequest) 

This is reproducible on Data Center: yes

Steps to Reproduce

1. Delete a repository
2. Whilst that repository is deleting attempt to update the name of a different repo

Expected Results

Users are able to update repositories whilst another is being deleted.

Actual Results

Server unreachable error is caused by a timeout when trying to update other repositories while waiting for `findByRepository` to complete.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available