[JIRAALIGN-1600] Cannot pull rank for features from capabilities in unassigned backlog.

Issue Summary

Rank can be pulled for features from capabilities in the assigned backlog, but not in unassigned backlog. It only shows pulling from Epics even when capabilities are turned on. 

Steps to Reproduce

1. Go to feature backlog in a portfolio w/ capabilities
2. Click on pull rank in any assigned backlog
3. Notice "Use Capabilities" 
4. Go to unassigned backlog slide out
5. Click Pull rank
6. Notice "Use epic rank"

Expected Results

Should use parent capability rank to sort features

Actual Results

Only shows "use epic rank" while the assigned backlog is using "capability rank

Workaround

None