[Tradfri] Workaround for lost commands

[sjsf]

PRs #4271, #4299 and #4388 all have tried working around the issue that under certain conditions commands get lost on gateway side by half-heartedly introducing and tweaking arbitrary delays.

This is to follow-up on them by finding a solution that reliably works around this issue until (if ever) the gateway's firmware gets fixed. The current approach is based on empirical observations with hardly an understanding for the root-causes and won't work reliably if there is another client interacting with the gateway.

See #4388 (comment) for the details of the discussion.