Adding config step to output the bisect config dictionary.

scripts/slave/recipes/bisect.expected/invalid_config_test.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "tryserver.chromium.perf",
       "--builder",
       "linux_perf_bisect_builder",
@@ skipping 56 matching lines @@
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
     "env": {
       "GYP_DEFINES": "branding=Chrome buildtype=Official component=static_library gomadir='[BUILD]/goma' target_arch=x64 use_goma=1"
     },
     "name": "gclient runhooks"
   },
   {
     "cmd": [
+      "echo",
+      "{'good_revision': 'XXX', 'builder_host': 'master4.golo.chromium.org', 'dummy_regression_confidence': '95', 'truncate_percent': '25', 'metric': 'warm_times/page_load_time', 'max_time_minutes': '5', 'builder_port': '8341', 'bug_id': '425582', 'command': 'tools/perf/run_benchmark -v --browser=release page_cycler.intl_ar_fa_he', 'poll_sleep': 0, 'dummy_builds': True, 'repeat_count': '2', 'test_type': 'perf', 'gs_bucket': 'chrome-perf', 'bad_revision': 'src@a6298e4afedbf2cd461755ea6f45b0ad64222222'}"
+    ],
+    "name": "config"
+  },
+  {
+    "cmd": [
       "git",
       "footers",
       "--position",
       "a6298e4afedbf2cd461755ea6f45b0ad64222222"
     ],
     "cwd": "[SLAVE_BUILD]/src",
     "name": "resolving hash a6298e4afedbf2cd461755ea6f45b0ad64222222",
     "stdout": "/path/to/tmp/"
   },
   {
     "name": "$final_result",
     "reason": "Could not parse commit position from git output: ",
     "status_code": 1
   }
 ]