Fix tree spawn at scale

The debrujin component is using an algorithm that doesn't respect the
previously assigned parent ID. This causes the other components to have
their routing trees broken whenever debrujin updates routes. This
happens whenever more than 256 nodes are involved, thus breaking tree
spawn for sizes >= 256

Thanks to @zrss for the report and diagnosis!

Signed-off-by: Ralph Castain <rhc@pmix.org>

Author: rhc54