Shiny updates: trigger "update success" message after unlocking, not before

[DavidAnderson]

In change-set https://core.trac.wordpress.org/changeset/32061 , an event was triggered upon completion of shiny updates.

This, I thought, solved the previous need for polling I had, in #31819. Further testing has revealed this to not be the case.

In fact, the real event I was trying to detect was not so much "update completed", as "lock released because updated completed".

Changeset 32061 added the trigger *before* releasing the lock (the lock release was immediately after). The attached patch moves the trigger to immediately *after* the lock release. So now, users of the trigger can know that the queue is unlocked, and respond accordingly.

(Alternatively, I suppose a second trigger could be added, so that both are covered. I'm not sure there's a use-case for this, though - I know there is for what I am trying to do, as it's for a live/popular plugin).

[DavidAnderson]

Move "update complete" trigger to after the queue has been unlocked

[jorbin]

In 32133:

Move wp-plugin-update-success event to after lock is released

Fixes #31978
See #31819
Props DavidAnderson