lambda-http does not set the correct x-ray trace id in the request

# Description
Request header 'X-Amzn-Trace-Id'  from lambda-http key is "Root=;, without **sample** and **parent** key

# Expected
X-Amzn-Trace-Id： Root=xxxx;Parent=xxxx;Sample=x;

# Environment
lambda_http = "0.7.0"