BTW the exact same behaviour can be detected in debian testing stretch:
[...]
24/4/2017 -- 11:40:45 - <Info> - dropped the caps for main thread
24/4/2017 -- 11:40:45 - <Error> - [ERRCODE: SC_ERR_FOPEN(44)] - Error
opening file: "/var/log/suricata//fast.log": Permission denied
24/4/2017 -- 11:40:45 - <Warning> - [ERRCODE:
SC_ERR_INVALID_ARGUMENT(13)] - output module setup failed
24/4/2017 -- 11:40:45 - <Error> - [ERRCODE: SC_ERR_FOPEN(44)] - Error
opening file: "/var/log/suricata//eve.json": Permission denied
24/4/2017 -- 11:40:45 - <Warning> - [ERRCODE:
SC_ERR_INVALID_ARGUMENT(13)] - output module setup failed
24/4/2017 -- 11:40:45 - <Error> - [ERRCODE: SC_ERR_FOPEN(44)] - Error
opening file: "/var/log/suricata//stats.log": Permission denied
24/4/2017 -- 11:40:45 - <Warning> - [ERRCODE:
SC_ERR_INVALID_ARGUMENT(13)] - output module setup failed
24/4/2017 -- 11:40:45 - <Info> - Going to use 8 thread(s)
24/4/2017 -- 11:40:45 - <Info> - Using unix socket file
'/var/run/suricata-command.socket'
24/4/2017 -- 11:40:45 - <Warning> - [ERRCODE:
SC_ERR_INITIALIZATION(45)] - Unix socket: UNIX socket
bind(/var/run/suricata-command.socket) error: Address already in use
24/4/2017 -- 11:40:45 - <Warning> - [ERRCODE:
SC_ERR_INITIALIZATION(45)] - Unable to create unix command socket
24/4/2017 -- 11:40:45 - <Info> - Unix socket: accept() error: Invalid argument
24/4/2017 -- 11:40:45 - <Notice> - all 8 packet processing threads, 4
management threads initialized, engine started.
24/4/2017 -- 11:40:45 - <Info> - Unix socket: accept() error: Invalid argument
24/4/2017 -- 11:40:45 - <Info> - Unix socket: accept() error: Invalid argument
24/4/2017 -- 11:40:45 - <Info> - Unix socket: accept() error: Invalid argument
24/4/2017 -- 11:40:45 - <Info> - Unix socket: accept() error: Invalid argument
24/4/2017 -- 11:40:45 - <Info> - Unix socket: accept() error: Invalid argument
24/4/2017 -- 11:40:45 - <Info> - Unix socket: accept() error: Invalid argument
24/4/2017 -- 11:40:45 - <Info> - Unix socket: accept() error: Invalid argument
24/4/2017 -- 11:40:45 - <Info> - Unix socket: accept() error: Invalid argument
24/4/2017 -- 11:40:45 - <Info> - Unix socket: accept() error: Invalid argument
[...]
