vswitch: Use consistent representation of DSCP bits.

vswitch: Use consistent representation of DSCP bits.

There are two sensible ways to represent the 6 DSCP bits of an IP
packet.  One could represent them as an integer in the range 0 to
63.  Or one could represent them as they would appear in the tos
field (0 to 63) << 2.  Before this patch, OVS had used the former
method for the DSCP bits in the Queue Table, and the latter for the
DSCP in the Controller and Manager tables.  Since the ability to
set DSCP bits in the Controller and Manager tables is so new that
it hasn't been released yet, this patch changes it to use the
existing style employed in the Queue table.  Hopefully this should
make the code and configuration less confusing.

Signed-off-by: Ethan Jackson <ethan@nicira.com>