add a configurable for disabling the auto-generated isolated RSA key

some users won't want to utilize the RSA key we auto-generate for
isolated node SSH access, but will instead want to manage SSH
authentication by hand outside of Tower

see: https://github.com/ansible/ansible-tower/issues/7380

awx/main/conf.py

@@ -205,6 +205,18 @@ register(
     category_slug='jobs',
 )
 
+register(
+    'AWX_ISOLATED_KEY_GENERATION',
+    field_class=fields.BooleanField,
+    default=True,
+    label=_('Generate RSA keys for isolated instances'),
+    help_text=_('If set, a random RSA key will be generated and distributed to '
+                'isolated instances.  To disable this behavior and manage authentication '
+                'for isolated instances outside of Tower, disable this setting.'),  # noqa
+    category=_('Jobs'),
+    category_slug='jobs',
+)
+
 register(
     'AWX_ISOLATED_PRIVATE_KEY',
     field_class=fields.CharField,