[ostf] size for bootable volume should be no less than image itself

[Dima Shulyak]

By default logic in ostf - default size for bootable volume is set to 1G,
which leads to inability to create a bootable volume with custom images.

Afaik it affects Mellanox team, and probably Sahara team as well, because they are using custom image.

Problem in this code:

https://github.com/stackforge/fuel-ostf/blob/master/fuel_health/nmanager.py#L303

Following code should be tweaked to account image size
https://github.com/stackforge/fuel-ostf/blob/master/fuel_health/nmanager.py#L888-894

[Dmitry Pyzhov (dpyzhov)]

We are lack of resources in 6.1

[Tatyanka (tatyana-leontovich)]

Move to invalid, we do not have cases covers bootable volume from other image then cirros. So for now there is not the problem at all