ospf6d: Set metric from default values when route-map metric not present

ospf6d: Set metric from default values when route-map metric not present

For redistribute commands if route map is set, then route takes it's metric
values from the route map. But in the case that routemap is set but the
metric for the route map is not, then the route metric is set to type-1.

Check if the metric is set for the routemap. If not then set it as per
redistributed default values (type 2)

Signed-off-by: Yash Ranjan <ranjany@vmware.com>