prevent instance group delete if running jobs

* related to https://github.com/ansible/ansible-tower/issues/7936

awx/main/models/ha.py

@@ -19,8 +19,12 @@ from awx.main.fields import JSONField
 from awx.main.models.inventory import InventoryUpdate
 from awx.main.models.jobs import Job
 from awx.main.models.projects import ProjectUpdate
-from awx.main.models.unified_jobs import UnifiedJob
+from awx.main.models.unified_jobs import (
+    UnifiedJob,
+    ACTIVE_STATES
+)
 from awx.main.utils import get_cpu_capacity, get_mem_capacity, get_system_task_capacity
+from awx.main.models.mixins import RelatedJobsMixin
 
 __all__ = ('Instance', 'InstanceGroup', 'JobOrigin', 'TowerScheduleState',)
 
@@ -110,7 +114,7 @@ class Instance(models.Model):
 
     
 
-class InstanceGroup(models.Model):
+class InstanceGroup(models.Model, RelatedJobsMixin):
     """A model representing a Queue/Group of AWX Instances."""
     objects = InstanceGroupManager()
 
@@ -152,6 +156,14 @@ class InstanceGroup(models.Model):
     def capacity(self):
         return sum([inst.capacity for inst in self.instances.all()])
 
+    '''
+    RelatedJobsMixin
+    '''
+    def _get_active_jobs(self):
+        return UnifiedJob.objects.filter(instance_group=self,
+                                         status__in=ACTIVE_STATES)
+
+
     class Meta:
         app_label = 'main'