Reduce initial bridge load by half

Instead of doing 2 (select + insert/update) queries for every insert,
do 1 query to get all the existing bridges. Iterate over all the
bridges, and set the ring. After this, insert or update all bridges
together. So running time reduces from O(2*n) to O(n).
Don't let distributors insert bridges

The splitter should do all the bridge insertion, not the dists. Remove
unnecesary functions.