get_url: Use atomic_move with get_url rather then shutil.copyfile

This brings get_url inline with the other internal file handling modules,
and allows replacement of in-use files.

lib/ansible/modules/net_tools/basics/get_url.py

@@ -526,8 +526,9 @@ def main():
             if backup:
                 if os.path.exists(dest):
                     backup_file = module.backup_local(dest)
-            shutil.copyfile(tmpsrc, dest)
+            module.atomic_move(tmpsrc, dest)
         except Exception as e:
+            if os.path.exists(tmpsrc):
                 os.remove(tmpsrc)
             module.fail_json(msg="failed to copy %s to %s: %s" % (tmpsrc, dest, to_native(e)),
                              exception=traceback.format_exc())
@@ -542,8 +543,6 @@ def main():
             os.remove(dest)
             module.fail_json(msg="The checksum for %s did not match %s; it was %s." % (dest, checksum, destination_checksum))
 
-    os.remove(tmpsrc)
-
     # allow file attribute changes
     module.params['path'] = dest
     file_args = module.load_file_common_arguments(module.params)