[FieldFormatters] Human-readable duration shows "a few seconds" when duration is "0"

[Dosant]

Kibana version: master (~7.14)
Describe the bug:

Human-readable duration field formatter outputs a few seconds for 0 value

Steps to reproduce:

1. Create a duration human-readable field formatter on index pattern
2. Check-in discover how a 0 value shown as a few seconds

Expected behavior:

I think we should output 0 following other formatting options. e.g. 0.00 seconds

Screenshots (if relevant):

Any additional context:

Noticed while testing #100540 (review)

[elasticmachine]

Pinging @elastic/kibana-app-services (Team:AppServices)

[rbrishabh]

Hey! I would like to take a shot at this! I'll create a PR