Even though vshCmddefOptParse() tried returning -1 if there was an
optional option specification that preceded a required one, it failed to
check that for boolean type options and options with VSH_OFLAG_REQ_OPT
flag set. On the other hand, it makes sense that VSH_OT_ARGV is
specified at the end of the option list.
Returning -1 enforces the proper ordering thanks to virsh-synopsis test
in 'make check'.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>