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",
+      "{\n  \"bad_revision\": \"src@a6298e4afedbf2cd461755ea6f45b0ad64222222\", \n  \"bug_id\": \"425582\", \n  \"builder_host\": \"master4.golo.chromium.org\", \n  \"builder_port\": \"8341\", \n  \"command\": \"tools/perf/run_benchmark -v --browser=release page_cycler.intl_ar_fa_he\", \n  \"dummy_builds\": true, \n  \"dummy_regression_confidence\": \"95\", \n  \"good_revision\": \"XXX\", \n  \"gs_bucket\": \"chrome-perf\", \n  \"max_time_minutes\": \"5\", \n  \"metric\": \"warm_times/page_load_time\", \n  \"poll_sleep\": 0, \n  \"repeat_count\": \"2\", \n  \"test_type\": \"perf\", \n  \"truncate_percent\": \"25\"\n}"
+    ],
+    "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
   }
 ]