Stop non-matching glob registration re-registering itself when receiving multiple navigation fetches

[ahume]

Register

navigator.registerServiceWorker('/foo/', 'worker.js');

Everytime /index.html with the above code loads it re-installs the worker. It does correctly ignore subsequent fetch events, bit it should only be installed once.

[tgvashworth]

I think the bug here is that we're getting registrations from the registry based on worker URL, not matched glob.