fix(ssr): inheritAttrs false adds attributes to html

[noreff]

Fix 11297.

After this fix inheritAttrs option works in a correct way and don't add attributes to html output.

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch for v2.x (or to a previous version branch), not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

[noreff]

Not sure what is the reason behind ci/circleci: test-cover shows me 1 broken test in completely unrelated area. Locally I have 0 errors after running npm run test

[noreff]

I made a little research about ci/circleci: test-cover failing, while local tests was passing. I found out that it did already happen before with a same test that is now failing for me. @posva wrote back than that it could be indeed failing because of a random thing and I have a filling that it does. I think that should be investigated further and be fixed. I can work on it, but I would be glad if some one verified first that it's needed.

[vhoyer]

lgtm