Description of problem:
When adding/editing provider or host with several Endpoints,
each Endpoint has a [Validate] button that should become disabled or enabled according to this Endpoint's fields.

Version-Release number of selected component (if applicable):
Problem appeared in Since https://github.com/ManageIQ/manageiq-ui-classic/pull/68, backported to euwe and darga.
Fixes just got merged on master, bug still happens on euwe and darga.

How reproducible: always

Steps to Reproduce:

1. Compute -> Containers -> Providers -> Configuration -> Add new / Edit
2. Fill all common fields and Default endpoint fields.
   Expected results: Default's [Validate] turns blue,
                     Hawkular's [Validate] should remain disabled grey.
   Actual results: Both Default & Hawkular are blue.
3. Fill all Hawkular fields, clear Default port.
   (note: do not clear Default token — it's also needed by Hawkular)
   Expected results: Default's [Validate] turns disabled grey,
                     Hawkular's [Validate] should become blue.
   Actual results: Both Default & Hawkular are grey.

Same with other multi-endpoint providers e.g. RHV.
Same with Hosts:

1. Compute -> Infrastructure -> Hosts/Nodes -> Configuration -> Add new / Edit Host
2. Fill common fields & Default Username.
   Expected: only Default [Validate] blue, Actual: all 4 blue.
3. Clear Default Username, fill other 3 Usernames
   Expected: Default [Validate] grey, other 3 blue, Actual: all 4 grey.

Additional info:
controller's changeAuthTab() was not getting called, so validation function always checked Default fields.
https://github.com/ManageIQ/manageiq-ui-classic/pull/706 fixes this.

master also required https://github.com/ManageIQ/manageiq-ui-classic/pull/713 fixing another bug making Hawkular [Validate] always disabled.
darga & euwe don't need this fix, 706 is enough.

So master just got fixed, but this needs 5.6, 5.7 clones to backport.