work around AAD service principal race condition (#716)

This works around an issue in AAD service principal creation.  The race condition in AAD shows up as:

```
INFO:deploy:checking if RBAC already exists
INFO:deploy:creating Application registration
INFO:deploy:creating service principal
Traceback (most recent call last):
  File "deploy.py", line 926, in <module>
    main()
  File "deploy.py", line 920, in main
    state[1](client)
  File "deploy.py", line 303, in setup_rbac
    client.service_principals.create(service_principal_params)
  File "/tmp/tmpp2x7ybfg/deploy-venv/lib/python3.8/site-packages/azure/graphrbac/operations/service_principals_operations.py", line 87, in create
    raise models.GraphErrorException(self._deserialize, response)
azure.graphrbac.models.graph_error_py3.GraphErrorException: When using this permission, the backing application of the service principal being created must in the local tenant
```

The azure-cli has the same issue, as seen in https://github.com/Azure/azure-cli/issues/14767

src/deployment/deploy.py

@@ -300,7 +300,33 @@ class Client:
                 service_principal_type="Application",
                 app_id=app.app_id,
             )
+
+            def try_sp_create() -> None:
+                error: Optional[Exception] = None
+                for _ in range(10):
+                    try:
                         client.service_principals.create(service_principal_params)
+                        return
+                    except GraphErrorException as err:
+                        # work around timing issue when creating service principal
+                        # https://github.com/Azure/azure-cli/issues/14767
+                        if (
+                            "service principal being created must in the local tenant"
+                            not in str(err)
+                        ):
+                            raise err
+                    logging.warning(
+                        "creating service principal failed with an error that occurs "
+                        "due to AAD race conditions"
+                    )
+                    time.sleep(60)
+                if error is None:
+                    raise Exception("service principal creation failed")
+                else:
+                    raise error
+
+            try_sp_create()
+
         else:
             app = existing[0]
             existing_role_values = [app_role.value for app_role in app.app_roles]