Add environment variables on filebeat start

[leslie]

I met the same problem as Filebeat Windows | Time sync using filebeat 6.4.2, so i downgrade to 6.0.0 .

the error is

2018-10-19T13:28:54+08:00 CRIT Exiting: missing field accessing 'fields.ip'

I want IP for some modules,however adding IP for every event is ok.