[Ceph] iSCSI gateway startup aborts with incompatible image features error

Issue

When attempting to bring up the iSCSI gateway, the following error can be seen in the journal:

Apr 16 13:21:47 mygwhost01 journal[1432182]: (LUN.allocate) rbd 'vmware-datastore-t4-elgh-linux' is not compatible with LIO#012Image features  are not supported
Apr 16 13:21:47 mygwhost01 journal[1432182]: iqn.2003-01.com.redhat.iscsi-gw:dgw - Could not define LUNs: Unable to register iscsi-tier/mydatastore with LIO: (LUN.allocate) rbd 'mydatastore' is not compatible with LIO#012Image features  are not supported
Apr 16 13:21:47 mygwhost01 journal[1432182]: Could not load gateway: Unable to register iscsi-tier/mydatastore with LIO: (LUN.allocate) rbd 'mydatastore' is not compatible with LIO#012Image features  are not supported
Apr 16 13:21:47 mygwhost01 journal[1432182]: Removing iSCSI target from LIO
Apr 16 13:21:47 mygwhost01 journal[1432182]: No available network portal for target with iqn of 'iqn.2003-01.com.redhat.iscsi-gw:dgw'