Rework version command to work with job wrappers that have not had 'prepare' executed.

Traditionally all synchronous job wrappers have had 'prepare' called when they are queued up, but prepare isn't called on the more transient job wrappers that are created in response to Pulsar asnchronous status update messages.

lib/galaxy/jobs/__init__.py

@@ -1035,7 +1035,7 @@ class JobWrapper( object ):
         else:
             final_job_state = job.states.ERROR
 
-        if self.write_version_cmd:
+        if self.tool.version_string_cmd:
             version_filename = self.get_version_string_path()
             if os.path.exists(version_filename):
                 self.version_string = open(version_filename).read()