jinja2: make 'import' return the leaf module instead of the root one

This is an incompatible change. For example, you would now write:

  import easy_install zc.buildout.easy_install

instead of:

  import zc zc.buildout.easy_install

slapos/recipe/template/jinja2_template.py

@@ -74,7 +74,8 @@ EXPRESSION_HANDLER = {
     'key': getKey,
     'json': (lambda expression, _, __, ___: json.loads(expression)),
     'jsonkey': getJsonKey,
-    'import': (lambda expression, _, __, ___: __import__(expression)),
+    'import': (lambda expression, _, __, ___:
+        __import__(expression, fromlist=['*'], level=0)),
     'section': (lambda expression, buildout, _, __: dict(
         buildout[expression])),
 }