[services] Tunnelbroker - Fix message from and to swap in AMQP tests

Summary:
This diff is a fix.

The constructor for the MessageItem entity was changed (fromDeviceID and `toDeviceID was swapped in places), but the tests have not reflected these changes. This diff fixes tests for the message items to reflect these changes.

Related Linear task: ENG-1491

Test Plan: Tests in DatabaseManagerTest.cpp was successfully built and passed in a sandbox.

Reviewers: karol, tomek

Reviewed By: karol, tomek

Subscribers: varun, ashoat, tomek, adrian, atul, karol, abosh

Differential Revision: https://phab.comm.dev/D4745