Continuously written log files corrupted using compression option

[struanb]

Having tried the compression option, we have had to disable it and implement separate gzipping logic.

Our log files are continuously written to, which meant the gzipped file was continuously written to as pm2-logrotate compression is implemented using pipes.

The current implementation seems broken, since when log files were renamed the resulting gzip files were truncated mid-gzip-stream. gunzipping them resulted in errors, and log files with truncated final lines.

A better implementation could be to write uncompressed logs, and gzip completed log files after their rotation.