Fix _update_volume_stats typos

Fix _update_volume_stats typos in 'cinder/volume/driver.py' and
'cinder/volume/drivers/eqlx.py'.
'_update_volume_status' to '_update_volume_stats'

Change-Id: I0642bdb911ca72517ed655f795e0055f4c4654b8
Closes-Bug: #1254978
Merge "Fix _update_volume_stats typos"