Add profiling support to glanceclinet

To be able to create profiling traces for Glance, client should be
able to send special HTTP header that contains trace info.
This patch is as well important to be able to make cross project
traces. (Typical case nova calls glance via python client, if
profiler is initialized in nova, glance client will add extra
header, that will be parsed by special osprofiler middleware in glance
api)
Don't worry no security issue here, trace information is signed by HMAC
key that is setted in api-paste.ini. So only person that knows HMAC key
is able to send proper header.

Change-Id: Ib13084fbe9b33c2f3dee165f7d6c778546cce6ca

glanceclient/common/http.py

@@ -39,9 +39,12 @@ import OpenSSL
 
 from glanceclient.common import utils
 from glanceclient import exc
+from glanceclient.openstack.common import importutils
 from glanceclient.openstack.common import network_utils
 from glanceclient.openstack.common import strutils
 
+osprofiler_web = importutils.try_import("osprofiler.web")
+
 try:
     from eventlet import patcher
     # Handle case where we are running in a monkey patched environment
@@ -175,6 +178,10 @@ class HTTPClient(object):
         # Copy the kwargs so we can reuse the original in case of redirects
         kwargs['headers'] = copy.deepcopy(kwargs.get('headers', {}))
         kwargs['headers'].setdefault('User-Agent', USER_AGENT)
+
+        if osprofiler_web:
+            kwargs['headers'].update(osprofiler_web.get_trace_id_headers())
+
         if self.auth_token:
             kwargs['headers'].setdefault('X-Auth-Token', self.auth_token)