qemu.tests: Update qmp_basic_rhel6.py according to qemu changes in rhel6.

Signed-off-by: Feng Yang <fyang@redhat.com>
qemu.tests: Add check SGABIOS info case for seabios.py

This patch add the restart vm function.

Changes from v2:
update some parameter name.

Signed-off-by: Shuping Cui <scui@redhat.com>
Signed-off-by: Yiqiao Pu <ypu@redhat.com>
Acked-by: Feng Yang <fyang@redhat.com>