[ci]: Cleanup the workspace

[xumia]

What I did
Cleanup the workspace.
Why I did it
In some of the test cases, it is run as root, left some of the file cannot be removed during the checkout step.

Example: https://dev.azure.com/mssonic/build/_build/results?buildId=71009&view=logs&j=3f6395b2-1619-5ebe-f305-2aedcf353cb5&t=aa8a4b4e-56c0-53e8-6540-01f05ca983a1

$ ls -l /agent/_work/1/s/tests/.pytest_cache/CACHEDIR.TAG
-rw-r--r-- 1 root root 194 Feb  8 13:28 /agent/_work/1/s/tests/.pytest_cache/CACHEDIR.TAG

$ ls -l /agent/_work/1/s/ -d
drwxr-xr-x 25 AzDevOps AzDevOps 4096 Feb  8 17:11 /agent/_work/1/s/

How I verified it

Details if related

[qiluo-msft]

sudo rm -rf $(ls -A1)

This combination has risk. For example there is a filename as 'a b', and rm will try rm a b which is removing two files.

And ls could output colors in ANSI sequence.

[xumia]

@qiluo-msft , the command is running before any script start, so it is to make the whole workspace clean. It is expected, there are no files as the agent hosted by Microsoft.
I changed the PR title and the description.

[xumia]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).