add a global config dictionary

There was no need for each test module to keep a copy for itself. This means we
can also get rid of test_set_init.
diff --git a/src/python/oftest/__init__.py b/src/python/oftest/__init__.py
index 802dc75..c1cbb78 100644
--- a/src/python/oftest/__init__.py
+++ b/src/python/oftest/__init__.py
@@ -1 +1,5 @@
 '''Docstring to silence pylint; ignores --ignore option for __init__.py'''
+
+# Global config dictionary
+# Populated by oft.
+config = {}