cfm: Log more aggressively amidst packet loss.

cfm: Log more aggressively amidst packet loss.

While debugging some issues today it became clear that it would be
useful to log when the CFM fault status changes and when packets
are lost.  The CFM module logs pretty aggressively when in debug
mode, but this can be chatty and most systems don't operate under
this logging level for extended periods of time.  This patch logs
when CCMs are received which indicate reordering or packet loss and
when the CFM fault status changed.

Requested-by: Jacob Cherkas <jcherkas@nicira.com>
Signed-off-by: Ethan Jackson <ethan@nicira.com>