ofproto-dpif: Log traces when resubmit depth is exceeded.

It can be very difficult to debug xlate_actions() failures due to
excessive resubmit recursion.  In an attempt to make it easier,
this patch adds a (severely rate-limited) full ofproto/trace to the
logs.

Suggested-by: Alan Shieh <ashieh@nicira.com>
Signed-off-by: Ethan Jackson <ethan@nicira.com>