Description of problem:

When creating new disk the default allocation policy is preallocated and user can check "is shareable" option. When switching to thin provision,the "is shareable" option turns to be greyed out. The problem is that when switching back to preallocated it stays greyed out. Basically once "is shareable" became greyed out it stays this way no matter what allocation policy you choose.  

Version-Release number of selected component (if applicable):


How reproducible:
100%


Steps to Reproduce:
1.Create new disk.
2.Notice that is shareable option not greyed out.
3.change allocation policy to thin provision. (notice that is shareable became greyed out)
4.change allocation policy to preallocated again.

is shareable stays greyed out.

Actual results:
When allocation policy is preallocated "is shareable" option checkable.
when allocation policy thin provision it's greyed out.

Expected results:


Additional info: