cfm: Clear RDI on new CFM configurations.

When CFM is first configured, it detects no remote endpoints, and
thus sets RDI on its CCMs.  This can cause the receiver of these
CCMs to think there is a problem when really things are simply
initializing.  This patch fixes the issue by not setting the RDI
bit in CCMs until at least one fault interval has passed.

Bug #12610.
Reported-by: Paul Ingram <paul@nicira.com>
Signed-off-by: Ethan Jackson <ethan@nicira.com>