Add retries to the InfraTests bot's "update go pkgs" step

infra/bots/recipes/swarm_infra.expected/infra_tests.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport sys, os\npath = sys.argv[1]\nmode = int(sys.argv[2])\nif not os.path.isdir(path):\n  if os.path.exists(path):\n    print \"%s exists but is not a dir\" % path\n    sys.exit(1)\n  os.makedirs(path, mode)\n",
       "[CUSTOM_/_B_WORK]",
       "511"
     ],
     "name": "makedirs checkout_path",
@@ skipping 111 matching lines @@
   {
     "cmd": [
       "go",
       "get",
       "-u",
       "go.skia.org/infra/..."
     ],
     "env": {
       "GOPATH": "[CUSTOM_/_B_WORK]/gopath"
     },
-    "name": "update_go_pkgs"
+    "name": "update go pkgs"
   },
   {
     "cmd": [
       "python",
       "[CUSTOM_/_B_WORK]/skia/infra/bots/infra_tests.py"
     ],
     "cwd": "[CUSTOM_/_B_WORK]/skia",
     "env": {
       "GOPATH": "[CUSTOM_/_B_WORK]/gopath"
     },
     "name": "infra_tests"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]