Avoid failure in case no port-forwards are present.
Without || true the result will be
ps aux
grep port-forw
grep -v grep
awk '{print $2}'
xargs --no-run-if-empty kill -9
kill: (15338): No such process

and the pipeline will forcefully stop.

Change-Id: I0b377e406567dc2dc154eed21216aa5b3f1ca8b1
diff --git a/jjb/pipeline/voltha/master/physical-build.groovy b/jjb/pipeline/voltha/master/physical-build.groovy
index fcffecf..5150ad5 100644
--- a/jjb/pipeline/voltha/master/physical-build.groovy
+++ b/jjb/pipeline/voltha/master/physical-build.groovy
@@ -76,7 +76,7 @@
           timeout(1) {
             sh returnStdout: false, script: '''
             # remove orphaned port-forward from different namespaces
-            ps aux | grep port-forw | grep -v grep | awk '{print $2}' | xargs --no-run-if-empty kill -9
+            ps aux | grep port-forw | grep -v grep | awk '{print $2}' | xargs --no-run-if-empty kill -9 || true
             '''
           }
         }