bug: Only try to delete ServiceAccount when it was created

[smuu]

{"level":"error","error":"error destroying pod for instance 'val0-f353122f': failed to delete service account: serviceaccounts \"val0-f353122f\" not found","name":"val0","time":"2024-05-06T16:26:29+02:00","message":"node  failed to cleanup"}
{"level":"error","error":"error destroying pod for instance 'val1-f82b49b7': failed to delete service account: serviceaccounts \"val1-f82b49b7\" not found","name":"val1","time":"2024-05-06T16:26:30+02:00","message":"node  failed to cleanup"}
{"level":"error","error":"error destroying pod for instance 'txsim0-5c2f636f': failed to delete service account: serviceaccounts \"txsim0-5c2f636f\" not found","name":"txsim0","time":"2024-05-06T16:26:31+02:00","message":"txsim failed to cleanup"}
{"level":"error","error":"error destroying pod for instance 'txsim1-b88885d0': failed to delete service account: serviceaccounts \"txsim1-b88885d0\" not found","name":"txsim1","time":"2024-05-06T16:26:32+02:00","message":"txsim failed to cleanup"}