chrony plugin does not track system time offset

[phemmer]

Bug report

Relevant telegraf.conf:

[[inputs.chrony]]

System info:

[Include Telegraf version, operating system name, and other relevant details]
version: 1.3.0
os: linux

Steps to reproduce:

1. run telegraf with chrony input enabled

Expected behavior:

data to indicate system clock offset from ntp server

Actual behavior:

no data indicates system clock offset from ntp server

Additional info:

In the chronyc tracking output, the System time field provides the clock offset.

# chronyc tracking
Reference ID    : 10.0.99.22 (ntp2.chewy.local)
Stratum         : 4
Ref time (UTC)  : Wed Jul 05 17:08:51 2017
System time     : 7495.370605469 seconds slow of NTP time
Last offset     : +0.000008273 seconds
RMS offset      : 344.988952637 seconds
Frequency       : 33.131 ppm slow
Residual freq   : +0.004 ppm
Skew            : 0.069 ppm
Root delay      : 0.033780 seconds
Root dispersion : 0.003258 seconds
Update interval : 1.9 seconds
Leap status     : Normal

However due to bug in the code, it tries to filter out the Ref time (UTC) field by looking for "time". This ends up filtering out the System time field as well.

[danielnelson]

Thanks @subfxnet