timeConstraints not preserved on default time value.

### I'm Submitting a ...
[x ] Bug report
[ ] Feature request
[ ] Support request
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### Steps to Reproduce
- Create a time constraint on hours, restricting the time from min 15 to max 18 with a step of 1.
- Click the time selector with timeFormat as 'hh:mm A'.
- Try the different options and observe that the time is not within 3pm to 6pm.
- Click the AM/PM button
- Observe the time constraints are now working

### Expected Results
I expect the default time to conform to the min timeConstraint bounds and show me 3pm by default instead of 12am.

### Actual Results
The default time is always 12am (00:00:00) regardless of the bounds. Your time constraints are in the PM, so there's also weird behaviour with how the picker resolves itself to the selectors. You have to click AM/PM manually to resolve the issues and get it into the correct bounds.

### Minimal Reproduction of the Problem
https://codepen.io/123spork/pen/MWYezdP

### Other Information (e.g. stacktraces, related issues, suggestions how to fix)
This is not simply a case of setting the default time value manually as I wish to use a placeholder on the input box provided. "Select Date" etc.

The simplest solution would be to utilise the minimum constraints (if they exist) in the default time value.