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
7cc2074885