Pass all zuul arguments to the job's shell script

The idea is that Zuul passes a lot of useful information, such as the
project name, target branch etc., as ZUUL_* options within the JSON job
data. Let's pass all of these variables to the launched shell script.
This will make it possible to e.g. have a single script that can do the
"right thing" for different projects with distinct build steps, etc.

Change-Id: I6f57ed19e9eef1b987fe2493d409b3ee51af22b6

turbo_hipster/lib/models.py

@@ -210,9 +210,14 @@ class ShellTask(Task):
                 'unique_id': self.job.unique
             }
         )
+
+        env_args = copy.deepcopy(os.environ)
+        env_args.update(self.job_arguments)
+
         self.script_return_code = utils.execute_to_log(
             cmd,
-            self.shell_output_log
+            self.shell_output_log,
+            env=env_args
         )
 
     @common.task_step