Jetpack Debug: Do not fail if WP.com SELF test times outs.

[kraftbj]

Fixes #12881

The "WP.com SELF Test" pings WordPress.com and requests the Jetpack.com/support/debug/ test suite ran, then reports the result. To allow time for all of the work, the HTTP timeout is increased to 30 seconds. Sometimes this isn't long enough either because the site is slow or simply slower to reach over the network.

Previously, a timeout when requesting the SELF test resulted in a test failure, reporting as such in the Site Health section of a WordPress site.

Now, a timeout will not fail out the test and won't be reported on Site Health.

Next steps would be evaluate this test and the REST API-based connection test to only require one.

Changes proposed in this Pull Request:

• Debug: Self test no longer fails on a timeout.

Is this a new feature or does it add/remove features to an existing part of Jetpack?

• n/a

Testing instructions:

• Add add_filter( 'http_request_timeout', function () { return 1; } ), 999 ); to your site (to reduce the HTTP timeout to 1 second.
• Visit the Tools->Site Health page.
• Prior to this PR, a really generic error would be reported for Jetpack.
• With this PR, no error is returned.

Proposed changelog entry for your changes:

• Debug: Reduce instances when an inconclusive response would result in an error.

[jetpackbot]

Thank you for the great PR description!

When this PR is ready for review, please apply the [Status] Needs Review label. If you are an a11n, please have someone from your team review the code if possible. The Jetpack team will also review this PR and merge it to be included in the next Jetpack release.

Scheduled Jetpack release: October 1, 2019.
Scheduled code freeze: September 24, 2019

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