virnetdevbandwidthtest: Reformat TC cmd line

virnetdevbandwidthtest: Reformat TC cmd line

Our coding style expects a long line to be broken into shorter
lines which are then aligned on the first character, for
instance:

  "some string that's broken "
  "into multiple lines"

However, one can argue that there are few cases where shifting
the alignment makes the code more readable. And this is the case
of expected cmd line for DO_TEST_SET() where a long cmd line can
be aligned on the arguments rather than the binary:

  TC " filter ..."
     " police ..."

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>