cros_build_lib.py: remove RuncommandCaptureOutput and RunCommandQuietly

RunCommandCaptureOutput is a wrapper of RunCommand. In multiple
places, we have a layer to decide whether to call RunCommand or
RunCommandCaptureOutput. There is no reason to have callers adding
logic to decide this. Move the logic into RunCommand by adding a
keyword argument 'capture_output'.

Also replace RunCommandQuietly by using keyword 'quiet'.

BUG=chromium:339596
CQ-DEPEND=CL:184474
CQ-DEPEND=CL:184478
TEST=`buildbot/run_tests`
TEST=trybot runs

Change-Id: Id6561467c868b9ecbbfa2d111ceb6b00999d68b2
Reviewed-on: https://chromium-review.googlesource.com/184448
Reviewed-by: David James <davidjames@chromium.org>
Tested-by: Yu-Ju Hong <yjhong@chromium.org>
Commit-Queue: Yu-Ju Hong <yjhong@chromium.org>
diff --git a/scripts/autotest_quickmerge.py b/scripts/autotest_quickmerge.py
index 97b525f..5ee17b3 100644
--- a/scripts/autotest_quickmerge.py
+++ b/scripts/autotest_quickmerge.py
@@ -83,8 +83,8 @@
     command.extend(['-path', os.path.join(path, ignore), '-prune', '-o'])
   command.extend(['-printf', r'%T@\n'])
 
-  command_result = cros_build_lib.RunCommandCaptureOutput(command,
-                                                          error_code_ok=True)
+  command_result = cros_build_lib.RunCommand(command, error_code_ok=True,
+                                             capture_output=True)
   float_times = [float(str_time) for str_time in
                 command_result.output.split('\n')
                 if str_time != '']