Check "auth event notification" param in log_json

[github at samba.org]

New comment by abartlet on Samba Github repository

https://github.com/samba-team/samba/pull/162#issuecomment-381003605
Comment:
Merged as 228d0430d59d26ae12d1f2ab7082f86fa10d5ba0 in master for Samba 4.9.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13381