ovs-ofctl: Fix replace-flows.

ovs-ofctl: Fix replace-flows.

The replace-flows test cases tested for incorrect
behavior due to the missing initialization of the out_group member of
struct ofputil_flow_stats_request.  This patch fixes this by properly
initializing out_group to OFPG_ANY.

Note that replace-flows still does not support multiple tables, but
that will be fixed in a later patch in the series.

Reported-by: YAMAMOTO Takashi <yamamoto@midokura.com>
Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: YAMAMOTO Takashi <yamamoto@midokura.com>