Change logging format for flows to that accepted by ofproto/trace.

Change logging format for flows to that accepted by ofproto/trace.

flow_format() logs packets contents.  However, the format used is not
the format accepted by ofproto/trace.  Hence it becomes difficult to
trace the packets using the debugs printed.  With this commit, the
logging of the packet contents is done in a format that is accepted
by ofproto/trace.  This will make debugging easier.

Signed-off-by: Mehak Mahajan <mmahajan@nicira.com>
Acked-by: Ethan Jackson <ethan@nicira.com>