Fix render of PATCH_CONTENT in full_json_patch krm function

This will fix Helm inline values patch rendering

When using inline values such as:

```
inline_values:
  service:
    ports:
      http: "8080"
      https: "8443"
```

The current `full_json_patch()` function was failing with error: `Error:
bad expression, please check expression syntax`. This is because yq
seems like doesn't properly handle literal new-lines inside a
double-quoted string.

This change replace current implementation to a safer approach using
HEREDOCS template to render the patch.

Change-Id: If7e78a6509ca0e6731f3125eeb535cedf394b06b
Signed-off-by: mesaj <juanmanuel.mesamendez.ext@telefonica.com>
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>