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

Related: OS#3047
Change-Id: If91b10d37cb4c940e009c12b232d042305d57886
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index 7d68736..c23bdec 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -17,5 +17,6 @@
 $MAKE $PARALLEL_MAKE
 $MAKE distcheck \
   || cat-testlogs.sh
+$MAKE maintainer-clean
 
 osmo-clean-workspace.sh