Simplify process of renaming a node prior to cluster join

I tried to create a cluster with an automation tool (not manually)

## Current Behavior

When i install couchDB in cluster mode, its mandorty to change default node name (couchdb@127.0.0.1) by FDQN in vm.args file. In this case, couchDB create a new node and keeps the first node active (couchdb@127.0.0.1).
To make the cluster work, i need to delete the first node. Not nice if i want to use an automation system like ansible.

## Possible Solution

When renaming node, replace the node name without adding a new one.

## Steps to Reproduce (for bugs)

1. Install couchDB with repositories (Debian)
2. Rename node in vm.args file
3. Restart couchDB daemon
4. View nodes in _membership URL

## Your Environment

Tried on Debian 9 with CouchDB 2.1.1

Reproduce the Debian setup by changing the node name in vm.args, restarting the CouchDB daemon, and inspecting the _membership URL. Trace how the existing node identity is handled during startup and verify that renaming replaces the default node rather than leaving both nodes active.

Written by the indexing model from the issue text.