Fixed formatting for command block

Hi, I just read through the FAQ and noticed the formatting on one of the examples was not correct. This is a small fix for that.

For visual diff please see the rendered markdown versions here:
https://github.com/openvswitch/ovs/blob/master/FAQ.md#q-what-destination-udp-port-does-the-vxlan-implementation-in-open-vswitch
https://github.com/scorpiion/ovs/blob/master/FAQ.md#q-what-destination-udp-port-does-the-vxlan-implementation-in-open-vswitch

Signed-off-by: Robert Åkerblom-Andersson <Robert.nr1@gmail.com>