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

Related: OS#3047
Change-Id: Ic147678e7906a8b9ad7fac8367602b656f4172e6
diff --git a/contrib/jenkins_amd64.sh b/contrib/jenkins_amd64.sh
index 9b83793..c79e26a 100755
--- a/contrib/jenkins_amd64.sh
+++ b/contrib/jenkins_amd64.sh
@@ -31,5 +31,6 @@
 DISTCHECK_CONFIGURE_FLAGS=--enable-external-tests \
     $MAKE distcheck \
     || cat-testlogs.sh
+$MAKE maintainer-clean
 
 osmo-clean-workspace.sh