The value of vRtrRsvpIfRefreshTime controls the interval
between the seccessive Path and Resv refresh messages.
RSVP declares the session down after it misses
((keep-multiplier + 0.5) * 1.5 * refresh-time)) consecutive
refresh messages.
When the value of vRtrRsvpIfRefreshTime is set to zero (0),
the value of vRtrRsvpGeneralRefreshTime is applied to that
specific RSVP interface.