To fix qemu-img and qemu-io binary path assignment

It seems the qemu-img and qemu-io sits in the same binary path of qemu-kvm if compiled locally, so going back one more folder level makes the wrong qemu-img path and hence switchs to default qemu-img path.
This patch checks for the qemu-img and qemu-io path in the same directory level where qemu-kvm path given from the command line.