Update voltctl jobs to 2c-4g

Change-Id: Ib9c849883527a4c288d2dcedcfbdad5ecf5351c2
diff --git a/jjb/verify/voltctl.yaml b/jjb/verify/voltctl.yaml
index ead09ef..9b586ab 100644
--- a/jjb/verify/voltctl.yaml
+++ b/jjb/verify/voltctl.yaml
@@ -20,6 +20,7 @@
       - 'tag-collision-reject':
           dependency-jobs: 'verify_voltctl_licensed'
       - 'make-unit-test':
+          build-node: 'ubuntu16.04-basebuild-2c-4g'
           unit-test-targets: 'lint sca test'
           unit-test-keep-going: 'true'
           dependency-jobs: 'verify_voltctl_tag-collision'