The value of vRtrMplsS2lSubLspMBBTimeoutIn specifies the amount of
time remaining, in seconds, for the in-progress S2L MBB path state to
time out after the initial PATH message has been sent. If the timer
expires and the in-progress S2L MBB path has not become operationally
up, the S2L MBB path is torn down and the retry timer is started to
schedule a new retry cycle.