This change should pick up the Host value from updated headers for 'Data to Sign'.

This change should pick up the Host value from updated headers for 'Data to Sign'. This change will also supports Akamai QA environment.

for Example:

    s = requests.Session()
    s.headers.update({'Host': 'akaa-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'})
    s.auth = EdgeGridAuth(...)

Since, Akamai QA environment requires us to update the host value in header, this module will pick up the updated host value for 'Data to Sign' to avoid Invalid signature error.