Fix use of aggregate mongodb command without 'cursor' option

[ansell]

Mongodb-3.4 deprecates the use of the aggregate command without using the cursor option.

https://docs.mongodb.com/manual/release-notes/3.4-compatibility/#aggregate-without-cursor

This would prevent upgrading to a maintained version of mongodb based on the notes above

It showed up as an issue in the log files when investigating profiles-service today:

==> /var/log/mongodb/mongod.log <==
2019-06-18T11:22:18.688+1000 W COMMAND  [conn5] Use of the aggregate command without the 'cursor' option is deprecated. See http://dochub.mongodb.org/core/aggregate-without-cursor-deprecation.