convert-upload-images-powervs script: Verify images by e.g. SHA value

[mgiessing]

If the RHEL bastion image link is not escaped ( & must be escaped to \&) the qcow2 file is downloaded incorrectly, but the script will continue.
Maybe a SHA value comparison can be used to verify the image.

[mkumatag]

/cc @sudeeshjohn @Shilpi-Das1

[mkumatag]

/cc @sudeeshjohn @Shilpi-Das1

any updates @sudeeshjohn @Shilpi-Das1 ?

[tsj-30]

/assign