Throttling issue with calls to user assigned managed identities

[chkeita]

Multiple exceptions in the service related to the query to get the user assigned managed identity resource

Exception while executing function: Functions.agent_commands Result: Failure
Exception: CloudError: Azure Error: 429
Message: Request is temporarily throttled because resource /subscriptions/ec0906f0-fc1f-4eae-9540-9b798d3f958c/resourcegroups/ansgoel-onefuzz/providers/Microsoft.ManagedIdentity/userAssignedIdentities/ansgoel-onefuzz-scalesetid has issued too many requests. Retry after 20 seconds.
Stack:   File "/azure-functions-host/workers/python/3.7/LINUX/X64/azure_functions_worker/dispatcher.py", line 349, in _handle__invocation_request
    self.__run_sync_func, invocation_id, fi.func, args)
  File "/usr/local/lib/python3.7/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/azure-functions-host/workers/python/3.7/LINUX/X64/azure_functions_worker/dispatcher.py", line 511, in __run_sync_func
    return func(**params)
  File "/home/site/wwwroot/agent_commands/__init__.py", line 53, in main
    return verify_token(req, m)
  File "/home/site/wwwroot/onefuzzlib/agent_authorization.py", line 76, in verify_token
    if not is_authorized(token):
  File "/home/site/wwwroot/.python_packages/lib/site-packages/memoization/caching/plain_cache.py", line 45, in wrapper
    result = user_function(*args, **kwargs)
  File "/home/site/wwwroot/onefuzzlib/agent_authorization.py", line 59, in is_authorized
    if get_scaleset_principal_id() == token_data.object_id:
  File "/home/site/wwwroot/.python_packages/lib/site-packages/memoization/caching/plain_cache.py", line 45, in wrapper
    result = user_function(*args, **kwargs)
  File "/home/site/wwwroot/onefuzzlib/azure/creds.py", line 146, in get_scaleset_principal_id
    uid = client.resources.get_by_id(get_scaleset_identity_resource_path(), api_version)
  File "/home/site/wwwroot/.python_packages/lib/site-packages/azure/mgmt/resource/resources/v2020_06_01/operations/_resources_operations.py", line 1304, in get_by_id
    raise exp