Description of problem:
I use this for creating direct lun
url:https://jl-rhevm31.rhev.lab.eng.brq.redhat.com/api/disks 
body:<disk>
    <name>direct_lun</name>
    <interface>virtio</interface>
    <format>cow</format>
    <lunStorage>
        <logical_unit id="36006048c12952607a6254682d950135a">
            <address>10.34.63.200</address>
            <port>3260</port>
            <target>iqn.1992-05.com.emc:ckm001201002300000-5-vnxe</target>
        </logical_unit>
    </lunStorage>
</disk>

which I think should have sufficient information for creating a direct lun. But it fails with 
<fault>
    <reason>Incomplete parameters</reason>
    <detail>Disk [provisionedSize|size] required for add</detail>
</fault>

From rsdl:
<parameter required="true" type="xs:int">
<name>provisioned_size</name>
</parameter>

Version-Release number of selected component (if applicable):
rhevm-restapi-3.1.0-15.el6ev.noarch

How reproducible:
Always

Steps to Reproduce:
1. Create direct lun without specifying size
  
Actual results:
Fails

Expected results:
Succeeds

Additional info:
I think the size should be taken from LUN itself and cannot be even overridden.