I'm trying insert a line in a property file using ansible.
I want to add some property if it does not exist, but not replace it if such property already exists in the file.

I add to my ansible role 

```
- name: add couchbase host to properties
  lineinfile: dest=/database.properties regexp="^couchbase.host"  line="couchbase.host=127.0.0.1"

```

But this replaces the property value back to 127.0.0.1 if it exists already in the file.

What I'm doing wrong?