TOML internal.Duration marshaller panics on integers

[denzuko]

Bug report

telegraf crashes with snmp input pointed to bigswitch

Relevant telegraf.conf:

'''
[[outputs.influxdb]]
urls = ["http://influxdbmaster:8086"] # required
database = "telegraf" # required

retention_policy = ""
write_consistency = "any"
timeout = "5s"

[[inputs.snmp]]
interval = "15s"
retries = 2
timeout = 5

version = 2
community="public"

agents = [ "bs1.example.tld", "bs2.example.tld" ]

[[inputs.snmp.table]]
name="bigswitch"

[[inputs.snmp.table.field]]
  name="memory"
  oid = ".1.3.6.1.4.1.25506.8.35.18.43.1.3"

'''

System info:

telegraf 1.0.0
influxdb 1.0.0
alpine linux

Steps to reproduce:

start telegraf

Expected behavior

Telegraf started and connected to influx

Actual behavior:

/ # telegraf
2016/10/21 20:39:22 Using config file: /etc/telegraf/telegraf.conf
panic: runtime error: slice bounds out of range

Additional info:

goroutine 1 [running]:
panic(0x12904a0, 0xc82000a050)
/usr/local/go/src/runtime/panic.go:481 +0x3e6
github.com/influxdata/telegraf/internal.(*Duration).UnmarshalTOML(0xc82014b7b8, 0xc8201a4a68, 0x1, 0x8, 0x0, 0x0)
/home/ubuntu/telegraf-build/src/github.com/influxdata/telegraf/internal/internal.go:39 +0x270
github.com/influxdata/toml.setUnmarshaler(0x1262080, 0xc82014b7b8, 0x199, 0xc8201a4a60, 0x1, 0x0, 0x0, 0xc8201a4a40)
/home/ubuntu/telegraf-build/src/github.com/influxdata/toml/decode.go:230 +0x2ec
github.com/influxdata/toml.setValue(0x1262080, 0xc82014b7b8, 0x199, 0x7f3ad67eeb18, 0xc8200136c0, 0x0, 0x0)

[phemmer]

timeout = 5

should be

timeout = "5s"

...or whatever your unit is if not seconds.

Agree this is a bug though. Parser should throw a graceful error rather than panic. Dunno that this'll get fixed though if the plan is to switch parsers (#1598).