Fix file.copy recipe_module to not fail if files are already equal.

scripts/slave/recipes/skia/swarm_test.expected/failed_get_hashes.json

Index: scripts/slave/recipes/skia/swarm_test.expected/failed_get_hashes.json
diff --git a/scripts/slave/recipes/skia/swarm_test.expected/failed_get_hashes.json b/scripts/slave/recipes/skia/swarm_test.expected/failed_get_hashes.json
index aaa631e0790ab80c10831ec58f8e307228a2ff6c..f923e717a8f8b959a3b23e456b230c1f7c65687c 100644
--- a/scripts/slave/recipes/skia/swarm_test.expected/failed_get_hashes.json
+++ b/scripts/slave/recipes/skia/swarm_test.expected/failed_get_hashes.json
@@ -271,7 +271,7 @@
     "cmd": [
       "python",
       "-u",
-      "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
+      "\nimport shutil\nimport sys\n# Apparently, shutil.copy fails if files are binary-equal on *nix OSes.\n# See http://crbug.com/636168#c8.\nif hasattr(shutil, '_samefile'):\n  if shutil._samefile(sys.argv[1], sys.argv[2]):\n    sys.exit(0)\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "[SLAVE_BUILD]/skia/infra/bots/assets/skp/VERSION",
       "/path/to/tmp/"
     ],
@@ -308,7 +308,7 @@
     "cmd": [
       "python",
       "-u",
-      "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
+      "\nimport shutil\nimport sys\n# Apparently, shutil.copy fails if files are binary-equal on *nix OSes.\n# See http://crbug.com/636168#c8.\nif hasattr(shutil, '_samefile'):\n  if shutil._samefile(sys.argv[1], sys.argv[2]):\n    sys.exit(0)\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "[SLAVE_BUILD]/skia/infra/bots/assets/skimage/VERSION",
       "/path/to/tmp/"
     ],