Adjusted test.py to use an installed vcs by default.

Adjusted test.py to use an installed vcs by default.

Protects agaist the off chance that the user doesn't have Arch (tla)
installed ;).

Changed Arch.name from "Arch" to "arch" so that each VCSs .name
matches the module name.  This allows us to use vcs.VCS_ORDER (a list
of module names) to set up the allowed values of BugDir.vcs_name.