Fixes RoonServer 2.71 in containers on QNAP.

- Work around vendor kernels whose syscall 452 is not fchmodat2 (RRD-2830):
  tar aborted with "Cannot change mode ...: Bad address" on the .roonhost
  alias symlinks, so neither a fresh install nor a self-update of 2.71 could
  complete. Detected at startup and scoped to tar; no effect on unaffected
  hosts. Verified on a TS-453Be (QTS 5.2.9 / 5.10.60-qnap), including a
  self-update that had been failing.

- Healthcheck: probe comm as well as cmdline, so 2.71's renamed head is
  recognised. Containers running 2.71 reported "unhealthy" on every
  platform despite Roon running normally.