Do not try to normalize size for zero size device factories
Do not try to normalize size for zero size device factories

Factories with zero size are special cases for adjusting container
size after removing a device for it. We don't want to change size
of the factory in this case.
The recent change of filesystem minimal size to 2 MiB resulted
in changing of size of these factories from 0 to 2 MiB which
caused the "adjusting factory" to create a new LV after removing
one from the container.

Resolves: rhbz#1743753

rvykydal/blivet,jkonecny12/blivet,jkonecny12/blivet,vojtechtrefny/blivet,vojtechtrefny/blivet,rvykydal/blivet