Functional tests: Fix brittle ID based tests

[boothj5]

Let functional tests increment unique ids, rather than hard code them, to make the tests a little less brittle.

[jubalh]

Currently we have functional tests disabled: 171b6e7

We should fix: profanity-im/stabber#5

We need it to have functional tests again. Which would be good to have, especially to test before the next release, since the many changes that came through OMEMO.

[DebXWoody]

I take it