License management UI is not screenreader accessible

[bhavyarm]

Kibana version: 6.3.0 BC3

Elasticsearch version: 6.3.0 BC3

Browser version: chrome latest

Browser OS version: OS X

Original install method (e.g. download page, yum, from source, etc.): from staging

Describe the bug: The page which gives you the details about your license is not screenreader accessible. Screenreader doesn't announce any details about the kind of license you have -
the only announcements are about buttons.

Steps to reproduce:

1. Enable voiceover or chromevox
2. Click on license management
3. Screenreader goes through the top padding and then jumps immediately into update license and revert to basic links.
4. Only if you click on the license info block - screenreader will announce the license information

I ran the aXe tool for accessibility and the error seems to be Axe Help :

Fix the following:
Required ARIA child role not present: tab

Expected behavior: User should be able to know their license information while tabbing and using screenreader.

[bhavyarm]

Same with uploading license page:

[bhavyarm]

@aphelionz can you please review this issue? Thanks!