ofproto: As of Open Flow 1.1 switch_features has no capabilities field

ofproto: As of Open Flow 1.1 switch_features has no capabilities field

In Open Flow 1.0 switch_features has a capabilities field.
However, in Open Flow 1.1, 1.2 and 1.3 this field is reserved.
Thus it should not be read on decode and it seems most appropriate
to set as zero on encode.

This patch takes the approach of setting the features field to
all available features for Open Flow 1.1+. I am unsure if it would
be sufficient to just set it to zero.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>