ospf6d: Fix distance command

ospf6d: Fix distance command

Reset prevoiusly configured distance command options
if user enters new (different) parameters.

Ticket:CM-19635
Reviewed By:
Testing Done:

R1(config-ospf6)# distance ospf6 intra-area 55 external 55
R1#show running-config ospf6d
router ospf6
 distance ospf6 intra-area 55 external 55

R1(config-ospf6)# distance ospf6 inter-area 55
R1#show running-config ospf6d
router ospf6
 distance ospf6 inter-area 55

Signed-off-by: Chirag Shah <chirag@cumulusnetworks.com>