Add timeout `status` to http spans.

[antonpirker]

Based on a slack thread - here's a snippet from @gggritso about behaviour that he would like to see for timeouts.

import urllib
import urllib.request

try:
    response = urllib.request.urlopen('http://python.org/', timeout=0.0001)
    html = response.read()
except urllib.error.URLError as e:
    print("URL Error", e.reason)
    if (e.reason == 'timed out'):
        span['status'] = 'time out'
        raise e

[szokeasaurusrex]

We can use deadline_exceeded as the span status.