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

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

Index: scripts/slave/recipes/skia/swarm_test.expected/big_issue_number.json
diff --git a/scripts/slave/recipes/skia/swarm_test.expected/big_issue_number.json b/scripts/slave/recipes/skia/swarm_test.expected/big_issue_number.json
index 063eb464093929016748008fd4771f2e2b85ad6b..1120debf146fe696a7d46cd745153f4f7a90276a 100644
--- a/scripts/slave/recipes/skia/swarm_test.expected/big_issue_number.json
+++ b/scripts/slave/recipes/skia/swarm_test.expected/big_issue_number.json
@@ -47,7 +47,7 @@
     "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/"
     ],
@@ -67,7 +67,7 @@
     "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/"
     ],