tests/promise/plugin: Adjust Amarisoft-related tests to match amarisoft_stats.json.log emitted by SR

In slapos@b32b4a8e `data` field in
that log switched from emitting objects via py repr to emitting them via
JSON. As the result, in particular, strings are now emitted quoted with
" instead of with ' .

-> Adjust all tests that simulate amarisoft_stats.json.log to follow
actual software-release behaviour.

The tests continue to pass.