Revert "Fix a typo."

This reverts commit 560787f3c58c5a7106ff3adaee8b7ad0e8ff26ab.
Revert "Remove an unnecessary variable initialization I added earlier."

This reverts commit 3c87090ceda882081ba46e91996f02fd3e11ca56.
Revert "- We must rlock the prefix list and wlock the router list (in that"

This reverts commit 33b2b206f18aa754fe612a7c9e395e22893181a7.
Revert "Add locking to the IPv6 prefix and default router lists."

This reverts commit 88d97786993b7bd2479338063d4e5ced7b2747bd.