Breaking change from Version 3.6.0 -> 3.6.1

**Describe the bug**
On existing couchdb clusters a upgrade from version 3.6.0 to 3.6.1 with default erlang cookie will fail.

**A clear and concise description of what the bug is.**
Commit 625d143 removes the default value "monster" in `couchdb/values.yaml ` for erlang cookie.
If no custom cookie value was defined in values.yaml, nodes cannot connect to existing cluster nodes.

**Version of Helm and Kubernetes**:
helm: v3.7.2
k8s: 1.23.8, 1.23.16 & 1.24.10

**What happened**:
Upgraded Pod will not start and cannot connect to cluster nodes.

**What you expected to happen**:
Upgrade should work.

**How to reproduce it** (as minimally and precisely as possible):
- take default values.yaml for version 3.6.0
- set cluster size to min 2
- deploy 3.6.0
- upgrade version to 3.6.1

**Anything else we need to know**:
Workaround:
Add erlang flags section into `values.yaml`

```yaml
erlangFlags:
name: couchdb
setcookie: monster
```