always chain failures

* When inv and proj updates trigger from a JT run, if either update
fails then the job template should get marked failed. Before this
commit, the job template would get marked failed ONLY if there was
enough capacity to run all the associated updates within the same
schedule() call. If, instead, the associated updates were ran in another
schedule() call, the failure chain was lost. This changeset fixes that
by saving the necessary data in the dependent_jobs relationship so that
the failure is always chained.

awx/main/models/unified_jobs.py

@@ -353,6 +353,10 @@ class UnifiedJobTypeStringMixin(object):
     def _underscore_to_camel(cls, word):
         return ''.join(x.capitalize() or '_' for x in word.split('_'))
 
+    @classmethod
+    def _camel_to_underscore(cls, word):
+        return re.sub('(?!^)([A-Z]+)', r'_\1', word).lower()
+
     @classmethod
     def _model_type(cls, job_type):
         # Django >= 1.9
@@ -371,6 +375,9 @@ class UnifiedJobTypeStringMixin(object):
             return None
         return model.objects.get(id=job_id)
 
+    def model_to_str(self):
+        return UnifiedJobTypeStringMixin._camel_to_underscore(self.__class__.__name__)
+
 
 class UnifiedJob(PolymorphicModel, PasswordFieldsModel, CommonModelNameNotUnique, UnifiedJobTypeStringMixin):
     '''