Update SAIO doc to have double proxy-logging in pipeline.

Change-Id: I0a034ca1420761cbf4e35dcea1d9cd18a92f90bd
Fix internal swift.source tracking.

In 1.8.0 (Grizzly), your proxy logs would indicate which middleware
was responsible for an internal request, e.g. TU for tempurl or BD for
bulk delete. At some point, those all turned into GET_INFO, which does
not give you any idea which specific middleware was responsible, only
that it came from a get_account_info/get_container_info call.

This commit puts it back to how it was in 1.8.0. Also, the
new-since-1.8.0 function get_object_info() got swift_source plumbing
added to it, so source tracking for the quota middlewares'
get_object_info() calls will happen now too.

Note that due to the new-since-1.8.0 in-environment caching of
account/container info, you may not see as many lines in the proxy log
as you would with 1.8.0. This is because there are actually fewer
internal requests being made.

Change-Id: I2b2ff7823c612dc7ed7f268da979c4500bbbe911
Merge "Update SAIO doc to have double proxy-logging in pipeline."