Handle lack of manifests/*.yml in shipit

Author: patjones

ci/scripts/shipit

@@ -123,6 +123,7 @@ if [[ -z $(git config --global user.name) ]]; then
 fi
 
 (cd ${REPO_ROOT}
+shopt -s nullglob
  for MANIFEST_PATH in manifests/*.yml; do
    len=$(wc -l $MANIFEST_PATH | awk '{print $1}')
    head=$(head -n `expr $len - 4` $MANIFEST_PATH)