tools: vshCmddefCheckInternals: Port mandatory options check from vshCmddefOptParse

tools: vshCmddefCheckInternals: Port mandatory options check from vshCmddefOptParse

'vshCmddefCheckInternals' is the go-to place for all checks related to
the definition of parameters for commands, but the check that all
mandatory parameters must be ordered before optional parameters was
still only in vshCmddefOptParse.

Adding a non-compliant option would not be caught by our test suite as
'virsh self-test' doesn't call vshCmddefOptParse.

Re-implement the check in vshCmddefCheckInternals.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>