qemu-iotests: use -nographic in test case 007

qemu-iotests: use -nographic in test case 007

A comment explains that -nographic hangs test case 007.  This is no
longer the case so add -nographic.  This makes the test suite faster and
more pleasant to run since no windows pop up.

I am not sure exactly when -nographic starting working for this case but
there is no fundamental reason why graphics are needed here.  Make sure
the serial port is not on stdio, it would conflict with the monitor.

Also remove unnecessary trailing whitespace on these lines.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Kevin Wolf <kwolf@redhat.com>