sw test tool: fix an error caused by changing enum name in of1.4

In openflow1.4 spec, enum name has become a changed as follows.

openflow1.3.4 spec:
     OFPR_NO_MATCH = 0, / * No matching flow (table-miss flow entry). * /

openflow1.4 spec:
     OFPR_TABLE_MISS = 0, / * No matching flow (table-miss flow entry). * /

Along with this change, AttributeError has occurred in the process of comparison of the received message.
This patch fixes this problem.

Signed-off-by: Minoru TAKAHASHI <takahashi.minoru7@gmail.com>