Change the default client polling interval to 1 hour

[fmarier]

In order to reduce the number of requests / sec we get, the server should tell clients to poll in 24 hours (86400 seconds).

[fmarier]

@ckolos suggested that we start by changing the polling interval to 1 hour first in order to get a feel for how much load it is when it's that frequent.

Note: it's important to keep it > 45 minutes because we want to make sure all of our testing happens with lists that are considered stale by the Safe Browsing protocol (where the 45 min magic value comes from).

[fmarier]

This is live in production:

$ ./download-list.py 
n:3600
i:mozstd-track-digest256
u:tracking-protection.cdn.mozilla.net/mozstd-track-digest256/1442352906