qemu: logrotate: drop minsize directive

qemu: logrotate: drop minsize directive

On a cloud host it is possible to create 100's of unique instances
per day, each leaving behind a /var/log/libvirt/qemu/instance-name.log
file that is < 100k. With the current 'minsize 100k' directive, these
files are never rotated and hence never removed. Over months of time,
tens of thousands of these files can accumulate on the host.

Dropping 'minsize 100k' allows rotating small files, which will
increase the number of log files, but 'rotate 4' ensures they will
be removed after a month.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>