Fix Dockerfile: use new format for ENV

```
1 warning found (use docker --debug to expand):

 - LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 9)

Dockerfile:3
```

Author: matriv

tests/client_tests/node-postgres/Dockerfile

@@ -6,7 +6,7 @@ RUN \
   apt-get update && \
   apt-get -y install python3-pip libpq5 libpq-dev sudo
 
-ENV HOME /root
+ENV HOME=/root
 WORKDIR /root
 USER jenkins