Discrepancy between spec and sdk implementation of should_sample

[srikanthccv]

Continuing from here https://cloud-native.slack.com/archives/C01PD4HUVBL/p1618175323112400.
Link to specification vs SDK

opentelemetry-python/opentelemetry-sdk/src/opentelemetry/sdk/trace/sampling.py

Lines 165 to 174 in 489a81e

	def should_sample(
	self,
	parent_context: Optional["Context"],
	trace_id: int,
	name: str,
	attributes: Attributes = None,
	links: Sequence["Link"] = None,
	trace_state: "TraceState" = None,
	) -> "SamplingResult":
	pass

The args list for should_sample in spec is different from python sdk implementation. This should be addressed.

[lzchen]

I don't think we can remove trace_state, as this will be a breaking change. span_kind should be added though.