Remove logcats from instrumentation test run steps.

scripts/slave/recipes/webrtc/standalone.expected/tryserver_webrtc_android_n6.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "tryserver.webrtc",
       "--builder",
       "android_n6",
@@ skipping 605 matching lines @@
     "name": "webrtc_perf_tests"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/webrtc/build/android/test_runner.py",
       "instrumentation",
       "--blacklist-file",
       "[SLAVE_BUILD]/src/out/bad_devices.json",
-      "--logcat-output-file",
-      "/path/to/tmp/",
       "--verbose",
       "--test-apk",
       "[SLAVE_BUILD]/src/out/Debug/apks/AppRTCDemoTest.apk",
       "--apk-under-test",
       "[SLAVE_BUILD]/src/out/Debug/apks/AppRTCDemo.apk"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "CHROMIUM_OUTPUT_DIR": "[SLAVE_BUILD]/src/out/Debug"
     },
     "name": "Instrumentation test AppRTCDemoTest"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/webrtc/build/android/test_runner.py",
       "instrumentation",
       "--blacklist-file",
       "[SLAVE_BUILD]/src/out/bad_devices.json",
-      "--logcat-output-file",
-      "/path/to/tmp/",
       "--verbose",
       "--test-apk",
       "[SLAVE_BUILD]/src/out/Debug/apks/libjingle_peerconnection_android_unittest.apk"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "CHROMIUM_OUTPUT_DIR": "[SLAVE_BUILD]/src/out/Debug"
     },
     "name": "Instrumentation test libjingle_peerconnection_android_unittest"
   },
@@ skipping 94 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  os.remove(report)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]