Move node builder for linters to ubuntu1804

issue with python3 version using ubuntu16.04

Issue-ID: INT-1478

Signed-off-by: mrichomme <morgan.richomme@orange.com>
Change-Id: Ie2dbe1c7d89520194a2ed842e993fd0add0e32b9
Signed-off-by: mrichomme <morgan.richomme@orange.com>
diff --git a/jjb/testsuite/testsuite.yaml b/jjb/testsuite/testsuite.yaml
index df3be18..4a8d9c9 100644
--- a/jjb/testsuite/testsuite.yaml
+++ b/jjb/testsuite/testsuite.yaml
@@ -63,7 +63,8 @@
     project-name: 'testsuite'
     python-version: python3
     jobs:
-      - '{project-name}-{stream}-{subproject}-lint'
+      - '{project-name}-{stream}-{subproject}-lint':
+          build-node: ubuntu1804-builder-4c-4g
     subproject:
       - 'yaml':
           tox-dir: '.'