Add a method to download and create a CentOS 7 image

The image is needed for scenario testing of Manila with CephFS as
backend. And download the image piece by piece where each piece is
of the size 100 MB to prevent overloading the memory.

Change-Id: Ib7101c59a4e955c7bc2aaa671d342169d6f0976d
Signed-off-by: Rishabh Dave <ridave@redhat.com>
1 file changed