exchange: improve setup time by using inotify to rsync only changed files

After this commit, the flow is something like:

# TODO add flow
1 job from topic/default/benchmark-push-pull in 2 minutes 59 seconds (queued for 2 seconds)
Status Job ID Name Coverage
failed #57726


Test tests-py2
 check the repos directory afterwards

ERROR: test-smoke-test.t output changed
Failed test-smoke-test-python3.t: output changed
Failed test-smoke-test.t: output changed
# Ran 11 tests, 0 skipped, 2 failed.
python hash seed: 1667155790
ERROR: Job failed: exit code 1