Bug 972188 - Don't call pair() for incoming file transfers
Revert "Bug 971648: Add warning message if there is no"

This reverts commit 70f3a23da3a89e00afda4eb3573de656b10d8ea0.
Revert "Bug 971648: Add warning message if there is no manifest.webapp"

This reverts commit 3c7e468f78843992a892ff036f470ceb260c6a07.
Merge pull request #16239 from svic/Bug_972188

Bug 972188 - Don't call pair() for incoming file transfers, r=evelyn
Bug 971473 - [System2] Instantiable CallForwarding

- update bootstrap_test
- add related tests for call_forwarding
- refactor call_forwarding