Users with no role on a site on a multisite network see inaccessible links in the admin toolbar

[johnbillion]

Previously, for single site installations: #25162

A user who is a member of a site on a multisite network but has no role on the site will encounter mostly the same problems as those which were fixed for single site users in #25162:

• An immediate "You do not have sufficient permissions" error upon logging in.
• An admin toolbar link to My Sites, which they cannot access.
• An admin toolbar link to their profile, which they cannot edit.
• An admin toolbar submenu link to the Dashboard of their site, which they cannot access.
• A link to the Dashboard from My Sites, which they cannot access (if they're a member of at least one site with a role).

[johnbillion]

Partial patch: 41453.patch​.

[johnbillion]

In 41796:

Users: Remove some links to the dashboard from My Sites for users who cannot access it.

See #41453

[johnbillion]

Closing as fixed for 4.9. Follow-up: #42315.