contrib/jenkins.sh: run "make maintainer-clean"

Related: OS#3047
Change-Id: I60c713a64ef629f0cb88121632ea6adc017fd0ae
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index 9777d4b..706ad5c 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -63,4 +63,5 @@
 	make -C "$base/doc/manuals" publish
 fi
 
+$MAKE maintainer-clean
 osmo-clean-workspace.sh