Remove top level clutter: move fixup_file_mtime (#3786)

Move this to .circlci where it's used.
Signed-off-by: Miek Gieben <miek@miek.nl>

.circleci/config.yml

@@ -45,7 +45,7 @@ jobs:
       - image: circleci/golang:1.13
     steps:
       - checkout
-      - run: ./fixup_file_mtime.sh
+      - run: ./.circleci/fixup_file_mtime.sh
       - run: make -f Makefile.doc
       - run: git diff --exit-code -- man/
   kubernetes-tests: