remove qcow3 cfg from guest-hw.cfg and add qcow2 V3 cfg in RHEL.7 host cfg

images created with -o compat=1.1 is still qcow2 formation, but Version 3

Signed-off-by: Xiaoqing Wei <xwei@redhat.com>
Merge branches 'origin/qcow2_v3' and 'origin/qcow2_v3'