tests: overhaul of newRandomVMIsWithMetrics
tests: overhaul of newRandomVMIsWithMetrics

Overhaul the `newRandomVMIsWithMetrics` helper: drop
redundant or unused return values, add argument (ignored atm) to make it
possible to prepare more than one VMI.

A future patch will extend further the function by launching  the
requested amount of VMIs on the same node.
We want to have VMIs all on the same noode in order to scrape just
one prometheus endpoint.

Signed-off-by: Francesco Romani <c7100b580e6017ef67482ace46578cdd2d2e0dfe@redhat.com>

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