[catapult] Set up android trybot on tryserver.client.catapult.

scripts/slave/recipes/catapult.expected/android.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "master.client.catapult",
       "--builder",
-      "windows",
+      "android",
       "--slave",
-      "windows_slave",
+      "android_slave",
       "--spec",
       "cache_dir = '[GIT_CACHE]'\nsolutions = [{'deps_file': 'DEPS', 'managed': True, 'name': 'catapult', 'url': 'https://chromium.googlesource.com/external/github.com/catapult-project/catapult.git'}]",
       "--root",
       "catapult",
       "--revision_mapping_file",
       "{\"catapult\": \"got_revision\"}",
       "--git-cache-dir",
       "[GIT_CACHE]",
       "--output_json",
       "/path/to/tmp/json",
@@ skipping 76 matching lines @@
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/catapult/catapult_build/build_steps.py",
       "--api-path-checkout",
       "[SLAVE_BUILD]/catapult",
       "--app-engine-sdk-pythonpath",
       "%(PYTHONPATH)s:[SLAVE_BUILD]/google_appengine",
       "--platform",
-      "linux",
+      "android",
       "--output-json",
       "/path/to/tmp/json"
     ],
     "cwd": "[SLAVE_BUILD]/catapult",
     "name": "gen step(build_steps.py)",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@[@@@",
       "@@@STEP_LOG_LINE@json.output@  {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"cmd\": [@@@",
       "@@@STEP_LOG_LINE@json.output@      \"run_py_tests\", @@@",
@@ skipping 11 matching lines @@
       "--no-hooks"
     ],
     "name": "Dashboard Tests"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]