Description of problem:
Make a template's boot source has a different storageclass of the default storageclass, create vm from this template, the storageclass of the VM disk is the default storageclass, not the one come from the template's boot source.

Version-Release number of selected component (if applicable):
v4.11.0-369

How reproducible:
100%

Steps to Reproduce:
1. the cluster default storageclass is HPP
2. upload a disk to a template with OCS
3. create vm from this template

Actual results:
the VM disk is using sc HPP.

Expected results:
the VM disk uses the storageclass OCS.

Additional info: