Fix logging isses

Closes yandex-sysmon/powny-cli#17
Closes yandex-sysmon/powny-cli#21
Closes yandex-sysmon/powny-cli#19
Closes yandex-sysmon/powny-cli#25
why not
```
for line in out_lines.split('\n'):
    if len(line):
        logger.log(level, prefix, line))
``` ?