Add '--adb-keys-file $HOME/.android/*.pub' to all bot provision_devices calls.

scripts/slave/recipes/chromium.expected/full_chromium_perf_Android_Nexus7v2_Perf.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "chromium.perf",
       "--builder",
       "Android Nexus7v2 Perf",
@@ skipping 191 matching lines @@
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/build/android/provision_devices.py",
       "-t",
       "Release",
+      "--adb-key-files /usr/local/google/home/navabi/.android/*.pub",
       "--min-battery-level",
       "95",
       "--disable-network",
       "--disable-java-debug"
     ],
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "provision_devices"
   },
@@ skipping 224 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@import glob, os, sys@@@",
       "@@@STEP_LOG_LINE@python.inline@for report in glob.glob(sys.argv[1]):@@@",
       "@@@STEP_LOG_LINE@python.inline@  with open(report, 'r') as f:@@@",
       "@@@STEP_LOG_LINE@python.inline@    for l in f.readlines():@@@",
       "@@@STEP_LOG_LINE@python.inline@      print l@@@",
       "@@@STEP_LOG_LINE@python.inline@  os.remove(report)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   }
 ]