Project Import failed even with Plugin installed in both Source and Target Instance.

Step to reproduce the error:

1. Install Greenhopper plugin on JIRA instance A using the UPM.
2. Install Greenhopper plugin with the same version on JIRA instance B using the UPM.
3. Create a project X on instance A
4. Backup instance A
5. Delete project X from A
6. Restore project X to JIRA instance B. It fails as shown in screenshot.

This step will not reproduce the error:

1. Install Greenhopper plugin on JIRA instance A using the UPM.
2. Install Greenhopper plugin with the same version on JIRA instance B using the UPM.
3. Restart JIRA instance A
4. Create a project Y on instance A
5. Backup instance A
6. Delete project Y from A
7. Restore project Y to JIRA instance B. It succeeds.

This is tested in JIRA 5.0.3.