fix(federation): give some time to prepare both servers
- when this background job runs, while the current server was not being
added as trusted_server in the other instance, yet, the secret sharing
would not be attempted again, without visual feedback.
- the change allows 5 attempts, which gives more than 20minutes to
complete. More do not really help as the endpoint is brute force
protected.
Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>