tests, restore tests: check on successful commands
tests, restore tests: check on successful commands

For some commands in the restore tests we expect prompt expression,
to verify the command execution. This could lead to unexpected behavior
as some commands will fail and notify their failure, but will return to
the console prompt, and the prompt expression will be matched.

This commit adds a `echo $?` after `mkdir` ,`echo` and
`chmod` commands, to avoid that.

An example can be found here:
https://prow.apps.ovirt.org/view/gcs/kubevirt-prow/pr-logs/pull/kubevirt_kubevirt/4010/pull-kubevirt-e2e-k8s-1.17-rook-ceph/1318094041715314688#1:build-log.txt%3A5281

Signed-off-by: alonSadan <17e3534da4e06ee40320bd1687715e3dda4806ac@redhat.com>

davidvossel/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,kubevirt/kubevirt,davidvossel/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,davidvossel/kubevirt,davidvossel/kubevirt,stu-gott/kubevirt