Bitbucket returns error 500 to JIRA DVCS due to expired memcache on Bitbucket Cloud

When JIRA DVCS connector is performing a long synchronisation from Bitbucket Cloud, memcache from Bitbucket side is expiring. Bitbucket returns error 500 to Jira.

Steps to Reproduce

1. In JIRA Software, link Bitbucket Cloud under the DVCS account configuration
2. JIRA will then start adding the corresponding repository
3. Under certain circumstances, sometimes JIRA fails to perform the synchronisation and Bitbucket Cloud returns error 500

Expected Results: Bitbucket doesn't return error 500

Actual Results:
JIRA DVCS connector is not aware of the memcache expiring and failed to re-establish a reconnection. During this event, Bitbucket returns error 500.

Corresponding Jira bug ticket: https://jira.atlassian.com/browse/JRASERVER-67936