Rename operation to operation_name

To help distinguish between operation objects and operation
names used in fileinfo.
Change signatures to require service/endpoint, not session

This allows for connection pool sharing across the tasks.

I think the long term goal is going to be to split fileinfo
from the s3 operations, but this should fix the fd leak
for the time being.
Fix integ tests with fileinfo signature changes
Remove set_session, it's no longer used
Merge branch 'conn-pool-leak' into develop

* conn-pool-leak:
  Remove set_session, it's no longer used
  Fix integ tests with fileinfo signature changes
  Change signatures to require service/endpoint, not session
  Rename operation to operation_name