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

Related: OS#3047
Change-Id: I6d541b47e68f5a8a61ac139a3ea85a9cb33856c1
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index dedec81..1dd8478 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -107,4 +107,5 @@
 	make -C "$base/doc/manuals" publish
 fi
 
+$MAKE maintainer-clean
 osmo-clean-workspace.sh