APPS-1780 Relax time regex

:koala:

So now
`0:6:43` will be the same as `00:06:43`
also `:6:43`

And `::43` will be the same as `00:00:43`
`::` will be `00:00:00`

/cc @zendesk/quokka 

### REFERENCE
- [JIRA APPS-1780](https://zendesk.atlassian.net/browse/APPS-1780)

### RISKS
- N/A
Worth DRY'ing this up into a helper function?
```js
function parseIntWithDefault(num, def) { return parseInt(num, 10) || def || 0; } 
```