Jetpack plugin installation fails after deactivating and deleting the full plugin

[dvdchr]

Refs pctCYC-Gx-p2#comment-748

Note:
This issue is out of scope but can be a potential improvement.

The scenario leading to the failure is:

• Have the self-hosted site connected with an individual plugin and the full plugin installed.
• Launch the app, and switch to the self-hosted site.
• Go to wp-admin on the browser, then deactivate & delete the full Jetpack plugin.
• Go back to the app, and go through the installation process.
• The installation fails due to the site losing its Jetpack connection from deactivating the full plugin.

When encountering this installation error, we might be able to identify the type of error (such as lost Jetpack connection) and provide a specific handling, such as offering to reestablish the connection (but the API state could make things tricky), or inform the app to refresh the site's state.