Run the metrics uploader in the background.

The metrics uploader was currently running on foreground where it
would copy the metrics files in a separate directory and then forked
into the background for the upload process. As a result, running the
lunch command would take a second longer to run since each metrics
uploader run had an average of half a second.

Bug: 140638454
Test: * Wrote and updated unit test cases.
      * Set ANDROID_ENABLE_METRICS_UPLOAD to point to the latest
        metrics_uploader bash script. Executed the "lunch 1" command
	and measured the running time. Executed "m nothing" command
	and checked that the metrics were uploaded.
      * Ran "lunch 1" and "m nothing" with
        ANDROID_ENABLE_METRICS_UPLOAD=""
      * Removed oauth from metrics_uploader and ran "m nothing" and
        "lunch 1". The oauth Message appeared only to "m nothing"

Change-Id: I13c61e666c8f44613dee291a704cef6a27335188
diff --git a/cmd/soong_ui/main.go b/cmd/soong_ui/main.go
index d0cad78..c965107 100644
--- a/cmd/soong_ui/main.go
+++ b/cmd/soong_ui/main.go
@@ -171,7 +171,7 @@
 	buildErrorFile := filepath.Join(logsDir, c.logsPrefix+"build_error")
 	rbeMetricsFile := filepath.Join(logsDir, c.logsPrefix+"rbe_metrics.pb")
 	soongMetricsFile := filepath.Join(logsDir, c.logsPrefix+"soong_metrics")
-	defer build.UploadMetrics(buildCtx, config, buildStartedMilli, buildErrorFile, rbeMetricsFile, soongMetricsFile)
+	defer build.UploadMetrics(buildCtx, config, c.forceDumbOutput, buildStartedMilli, buildErrorFile, rbeMetricsFile, soongMetricsFile)
 
 	os.MkdirAll(logsDir, 0777)
 	log.SetOutput(filepath.Join(logsDir, c.logsPrefix+"soong.log"))