* use the init.defaultBranch name, not master
* make tcl and modules/common independent
Both used to use not just the same directory, but the same *file* for
their outputs. In parallel this can cause problems, but it can also
accidentally allow expected failures to pass if the file is left around
by mistake.
* use a non-global misc_cache in tests
* make pkg tests resilient to gitignore
* make source cache and module directories non-global