Add profiling support to cinderclient

To be able to create profiling traces for Cinder, 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 cinder via python client, if
profiler is initialized in nova, cinder client will add extra
header, that will be parsed by special osprofiler middleware in cinder
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.

Main patch (in Cinder) is:
https://review.openstack.org/#/c/103415/

Change-Id: I53bb1b92e62841a02f941bdafaed7f8ed5db7ce1