misc: ipfix process node wait time adjustment

misc: ipfix process node wait time adjustment

Type: fix

The ipfix process node has a hardcoded 5s sleep between sending packets.
The interval between template packets is configurable, but the timing
of packets being sent does not match configuration because of the time
being hardcoded. E.g. -

With template interval set to 3s, a packet will be sent every 5s.
With template interval set to 8s, a packet will be sent every 10s.

Honor the configuration by reducing the wait time to less than 5s if a
template will need to be sent less than 5s from the current time.

Change-Id: I8c11f7bc502ce5b20b6e82a7e7a135a8805a2bad
Signed-off-by: Matthew Smith <mgsmith@netgate.com>