add regtest script and conf

Change-Id: Ieb82235bd6b436b6716992c1b45698b083d03d86

remove pre-existing chef files before uploading new chef files.

having legacy stale chef roles/cookbooks/databags in the knife
source directory will result in possible failure of dependency check,
so gurantee we have the latest code in that directory.

clean installation logs when refresh database.

Change-Id: I6609e90e51d8ca3560f1848f2de62e148f0c5b49