After discussion with DB we decided to rename the new iolimit
element as it creates the impression it would be there to
limit (i.e. throttle) I/O instead of specifying immutable
characteristics of a block device.
This is also backed by the fact that the term I/O Limits has
vanished from newer storage admin documentation.
Signed-off-by: NViktor Mihajlovski <mihajlov@linux.vnet.ibm.com>