OSprofiler in Swift

Spec in oslo [1] describes most of points and use cases of OSprofiler.
Short summary:
 - OSprofiler is a cross service profiler.
 - It is already supported and used in several OpenStack projects(nova, cinder, neutron, glance, heat and etc).
 - There is no performance impact in case of disabled OSprofiler. Just simple check "if osprofiler is not None".
 - Patches which add support of OSprofiler to nova are almost ready and waiting for your attention and review.

Blueprint in Nova: https://blueprints.launchpad.net/nova/+spec/osprofiler-support-in-nova
Patch in Nova: https://review.openstack.org/#/c/254703/

In history, swift also had a patch [2] (abandoned) related to tracing.

[1] https://specs.openstack.org/openstack/oslo-specs/specs/mitaka/osprofiler-cross-service-project-profiling.html
[2] https://review.openstack.org/#/c/93677/