test qgraph.c: Fix segs due to out of scope default

test qgraph.c: Fix segs due to out of scope default

The test uses the trick:
   if (!opts) {
     opts = &(QOSGraph...Options) { };
   }

  in a couple of places, however the temporary created
by the &() {}  goes out of scope at the bottom of the if,
and results in a seg or assert when opts-> fields are
used (on fedora 30's gcc 9).

Fixes: fc281c802022cb3a73a5
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190405184037.16799-1-dgilbert@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>