virsh.dump: Add a negative case and typo fix

Signed-off-by: Yanbing Du <ydu@redhat.com>
virsh.dump: Add tests for including/excluding KVM guest OS memory

Signed-off-by: Yanbing Du <ydu@redhat.com>
Merge pull request #232 from will-Do/dump

virsh.dump:  Case expend and bug fix