Does not respect the hour limits when pressing the AM/PM selector

### I'm Submitting a ...

```
[x] Bug report
[ ] Feature request
[ ] Support request
```

### Steps to Reproduce

1- Create an instance of react-datetime with the time format as "hh:mm A" and the min and max hours as 8 and 18 respectively
2 - Run the project
3 - Change the hour selecting by pressing only the upwards arrow in the 'AM/PM' selector
4 - The hour limits are not respected
### Expected Results

It should respect the hour limits when changing through the AM/PM selector
### Actual Results

### Minimal Reproduction of the Problem

Here is the codepen
https://codepen.io/Damianed/pen/eYYypaR

The hour should no got pass 6 PM and it works fine when pressing the hour arrows but it doesn't when presssing the AM/PM arrows

Reproduce the issue using the linked CodePen with the "hh:mm A" format and hour limits of 8 and 18. Trace the hour and AM/PM selector behavior, then verify that changing AM/PM never moves the selected time past 6 PM while the existing hour arrows continue to work.

Written by the indexing model from the issue text.