We previously rejected removing the number of replicas setting, which
prevents users from reverting this setting to its default the natural
way. To fix this, we put back the setting with the default value in the
cases that the user is trying to remove it. Yet, we also need to do the
work of updating the routing table and so on appropriately. This case
was missed because when the setting is being removed, we were defaulting
to -1 in this code path, which is treated as not being updated. Instead,
we must treat the case when we are removing this setting as if the
setting is being updated, too. This commit does that.
7c8860b7e6