Reduce api log rotation parameters

The log file configured in nova api and nova metadata are only used to
pass the data to the log sidecar, which then outputs the data to stdout
and then goes to /var/log/pods and/or a centralized logging service.

Considering this, there is no need to keep 5 rotated logs, since we'll
also have them in the other locations and there is no way to get them
without actually going manually into the specific container within the
pod.

This patch proposes having a single rotated log (because passing 0 as
max_logfile_count doesn't work as we want in oslo.log) and reducing the
size to rotate from 50MB to 20MB.

templates/nova.conf

@@ -5,8 +5,8 @@ max_concurrent_live_migrations=1
 state_path = /var/lib/nova
 allow_resize_to_same_host = true
 # enable log rotation in oslo config by default
-max_logfile_count=5
-max_logfile_size_mb=50
+max_logfile_count=1
+max_logfile_size_mb=20
 log_rotation_type=size
 {{if (index . "log_file") }}
 log_file = {{ .log_file }}