log rotate: do NOT overwrite file with possible writers

log rotate: do NOT overwrite file with possible writers

this is not the job of logrotate, and the real 20+ years battle
tested log rotate binary does not do so either as it's actually
pretty dangerous.

If we "replace" the file we break any logger which already opened a
new one here, e.g., a dameon starting up, and thus that writer would
log to nirvana.

It's the job of a logger to create a file if not existing, it makes
no sense to do it here.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>