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
Merge "Add profiling support to glanceclinet"