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

Related: OS#3047
Change-Id: I0ad159a3973d28ac79ea7fb433401c72b247c2b0
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index b512334..2c03c09 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -60,4 +60,5 @@
 	make -C "$base/doc/manuals" publish
 fi
 
+$MAKE maintainer-clean
 osmo-clean-workspace.sh