core: Remove version 2.2 checks in DataCenterStorageListModel

Removes version 2.2 checks related to storage format type in
DataCenterStorageListModel.

Change-Id: Ida6c034172e797ab4460cd954958663e4d112c12
Bug-Url: https://bugzilla.redhat.com/1127590
Signed-off-by: Martin Perina <mperina@redhat.com>