Timestamp in logs use mixed timezone

[gyscos]

The log file from telegraf includes a timestamp for each entry. However, this timestamp is sometimes using the local timezone, and sometimes using UTC.

Here is an example from the logs (where the local timestamp is America/Los_Angeles):

2017-06-22T21:00:03Z I! Starting Telegraf (version 1.3.2)
2017-06-22T21:00:03Z I! Loaded outputs: influxdb
2017-06-22T21:00:03Z I! Loaded inputs: inputs.cpu inputs.system inputs.nginx inputs.logparser inputs.logparser inputs.logparser
2017-06-22T21:00:03Z I! Tags enabled: host=www3 machine=www3
2017-06-22T21:00:03Z I! Agent Config: Interval:15s, Quiet:false, Hostname:"www3", Flush Interval:15s 
2017/06/22 14:00:03 Seeked /var/log/nginx/timing_a.log - &{Offset:0 Whence:2}
2017/06/22 14:00:03 Seeked /var/log/nginx/timing_b.log - &{Offset:0 Whence:2}
2017/06/22 14:00:03 Seeked /var/log/nginx/timing_c.log - &{Offset:0 Whence:2}

[danielnelson]

These are emitted by the hpcloud/tail library, I'll apply hpcloud/tail#120 to our fork.