Select control of FormGroup to be invalid if select value are different from the given option.

[ionitron-bot]

Original issue by @ejaz47 on 2018-02-16T05:01:33Z

Ionic version:
(For Ionic 1.x issues, please use https://github.com/ionic-team/ionic-v1)
[x] 2.x
[x] 3.x

I'm submitting a ... (check one with "x")
[x] bug report
[x] feature request

Current behavior:
As per the standard in HTML you can not set a value(which is not available in option) of select control even from Javascript.
Setting any value for the Select control of FormGroup always gives valid which is unexpected.

Expected behavior:
Select control of FormGroup to be invalid if select value are different from the given option.

Steps to reproduce:
working Plunker link.

Other information:
I have already asked it on Stack overflow