smoketest: T4576: add guard timeout for systemd in log level tests (#4142)
Systemd comes with a default of 5 restarts in 10 seconds policy, this limit can
be hit by this reastart sequence, slow down a bit.
(cherry picked from commit 810d9a819ee378460a05ed6c7e064fb105058fc2)
Co-authored-by: Christian Breunig <christian@breunig.cc>