Cannot create a volume from an image after the image's properties were edited

[Yogev Rabl]

Description of problem:
The creation of a volume from an image failed after the minimum RAM, minimum disk and shared properties have been edited.
Cinder was able to create a volume from images that their properties were not edited (and were different than 0)

Version-Release number of selected component (if applicable):
python-cinder-2015.1.0-2.el7ost.noarch
python-cinderclient-1.1.1-1.el7ost.noarch
openstack-cinder-2015.1.0-2.el7ost.noarch
openstack-glance-2015.1.0-6.el7ost.noarch

How reproducible:
100%

Steps to Reproduce:
1. Create an image
2. Edit the image properties (min. RAM/Disk or shared/protected)
3. Create a volume from the image

Actual results:
In the Horizon the error message is: Error: Unable to create volume.
In the CLI the error is:
ERROR: Internal Server Error (HTTP 500) (Request-ID: req-1afecc0d-2647-4387-83cc-11ba214b2cad)

Expected results:
A new volume can be created from any image

Additional info:
attached: the error from the cinder's api log