OpenTracing propagator does not use a TraceFlags object

[ocelotl]

I set up a client and server that propagated spans using the OpenTracing propagator. The server side reported this error:

[2021-04-26 16:41:13,377] ERROR in app: Exception on /ping [GET]
Traceback (most recent call last):
  File "/home/ocelotl/virtual_environments/LS-22507/lib/python3.8/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/ocelotl/virtual_environments/LS-22507/lib/python3.8/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/ocelotl/virtual_environments/LS-22507/lib/python3.8/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/ocelotl/virtual_environments/LS-22507/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/home/ocelotl/virtual_environments/LS-22507/lib/python3.8/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/ocelotl/virtual_environments/LS-22507/lib/python3.8/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "server.py", line 53, in ping
    with tracer.start_as_current_span(
  File "/home/ocelotl/.pyenv/versions/3.8.3/lib/python3.8/contextlib.py", line 113, in __enter__
    return next(self.gen)
  File "/home/ocelotl/github/ocelotl/opentelemetry-python/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py", line 863, in start_as_current_span
    span = self.start_span(
  File "/home/ocelotl/github/ocelotl/opentelemetry-python/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py", line 917, in start_span
    sampling_result = self.sampler.should_sample(
  File "/home/ocelotl/github/ocelotl/opentelemetry-python/opentelemetry-sdk/src/opentelemetry/sdk/trace/sampling.py", line 326, in should_sample
    if parent_span_context.trace_flags.sampled:
AttributeError: 'int' object has no attribute 'sampled'

This happens because when instantiating a context during propagation with the OpenTracing propagator, a TracFlags object is not used for the trace flags.