bfdd: fix detection timeout update

bfdd: fix detection timeout update

Per RFC 5880 section 6.8.12, the use of a Poll Sequence is not necessary
when the Detect Multiplier is changed. Currently, we update the Detection
Timeout only when a Poll Sequence is terminated, therefore we ignore the
Detect Multiplier change if it's not accompanied with RX/TX timer change.
To fix the problem, we should update the Detection Timeout on every
received packet.

Signed-off-by: Igor Ryzhov <iryzhov@nfware.com>
(cherry picked from commit 074f76812bb1961a5d8a4e7b01d7f70f5da1978b)