Encode toml durations correctly

[corylanou]

Fixes #2144

[corylanou]

Durations are now encoded properly. Running influxd config will give you this now:

hostname = "Corys-MacBook-Pro.local"
bind-address = ""
reporting-disabled = false

[initialization]
  join-urls = ""

[authentication]
  enabled = false

[admin]
  enabled = true
  port = 8083

[api]
  port = 0
  ssl-port = 0
  ssl-cert = ""
  read-timeout = "0"

[collectd]
  address = ""
  port = 0
  database = ""
  enabled = false
  typesdb = ""

[udp]
  enabled = false
  bind-address = ""
  port = 0

[broker]
  port = 8086
  dir = "/Users/corylanou/.influxdb/broker"
  election-timeout = "1s"

[data]
  dir = "/Users/corylanou/.influxdb/data"
  port = 8086
  retention-auto-create = true
  retention-check-enabled = true
  retention-check-period = "10m0s"
  retention-create-period = "45m0s"

[Snapshot]
  enabled = true
  bind-address = "127.0.0.1"
  port = 8087

[cluster]
  dir = ""

[logging]
  write-tracing = false
  raft-tracing = false

[Statistics]
  enabled = false
  database = "_internal"
  retention-policy = "default"
  write-interval = "1m0s"

[continuous_queries]
  recompute-previous-n = 2
  recompute-no-older-than = "10m0s"
  compute-runs-per-interval = 10
  compute-no-more-than = "2m0s"
  disable = false

[otoolep]

Let's make this something like "...which fixes default configuration generation."

[otoolep]

+1, minor suggestion re changelog.