BlobStore plugin dark features in OnDemand causes Attachments to display a 500 error in JIRA when migrating from OD to Server

In JIRA OnDemand there's a new plugin that manages the attachments - Atlassian BlobStore Client Plugin.

This plugin is currently not available for JIRA Server (Behind the Firewall), and when migrating JIRA from Cloud (OnDemand) to Server (BTF) JIRA is not able to display attachments. It throws a 500 error instead.

Steps to Replicate the Problem:

1. Export a JIRA Cloud backup;
2. Install JIRA Server 6.3.4;
3. And restore the Cloud backup (XML + /data/ folder);
4. Try to access an attachment.

Expected Behavior:

The attachments is displayed correctly.

Actual Behavior:

JIRA shows a 500 error page. In the logs, the following is thrown:

2014-09-04 19:10:20,824 http-bio-8080-exec-1 ERROR jtabeling 1150x15324x1 1xp3ogl 192.168.10.XX,127.0.0.1 /secure/attachment/10405/MyScreenshot.png [jira.web.servlet.ViewAttachmentServlet] Error serving file for path /10405/MyScreenshot.png: BlobStore Client Plugin not loaded
java.lang.IllegalStateException: BlobStore Client Plugin not loaded
	at com.atlassian.jira.issue.attachment.BlobStoreAttachmentStore.getBlobStore(BlobStoreAttachmentStore.java:45)
	at com.atlassian.jira.issue.attachment.BlobStoreAttachmentStore.get(BlobStoreAttachmentStore.java:57)

Workaround:

As per Accessing Attachments show a 500 error page after migration from OnDemand, please:

1. Access the Dark Features page in the JIRA Server through http://<jira-address>/secure/admin/SiteDarkFeatures!default.jspa
2. Disable the com.atlassian.jira.FS_ATTACHMENTS_PRIMARY dark feature.