Fix handling of environment inheritence, and template each inherited env

Environments were not being templated individually, so a variable environment
value was causing the exception regarding dicts to be hit. Also, environments
as inherited were coming through with the tasks listed first, followed by the
parents, so they were being merged backwards. Reversing the list of environments
fixed this.

lib/ansible/plugins/action/__init__.py

@@ -151,14 +151,19 @@ class ActionBase(with_metaclass(ABCMeta, object)):
             if not isinstance(environments, list):
                 environments = [ environments ]
 
+            # the environments as inherited need to be reversed, to make
+            # sure we merge in the parent's values first so those in the
+            # block then task 'win' in precedence
+            environments.reverse()
             for environment in environments:
                 if environment is None:
                     continue
-                if not isinstance(environment, dict):
-                    raise AnsibleError("environment must be a dictionary, received %s (%s)" % (environment, type(environment)))
+                temp_environment = self._templar.template(environment)
+                if not isinstance(temp_environment, dict):
+                    raise AnsibleError("environment must be a dictionary, received %s (%s)" % (temp_environment, type(temp_environment)))
                 # very deliberately using update here instead of combine_vars, as
                 # these environment settings should not need to merge sub-dicts
-                final_environment.update(environment)
+                final_environment.update(temp_environment)
 
         final_environment = self._templar.template(final_environment)
         return self._connection._shell.env_prefix(**final_environment)