[BUG] manager fails to start when "report_stats" is not in conf (v2 format)

[frikilax]

Describe the bug
manager always try to access "report_stats" in configuration when in v2 format, but "report_stats" is not a required field.

Plateform (please complete the following information):

• OS FreeBSD 12.0
• Darwin version: 1.2.1

To Reproduce
Steps to reproduce the behavior:

1. Generate a conf with v2 format (see doc)
2. don't put any "report_stats" field
3. start the manager

Expected behavior
the manager should start while setting no stats reporting