Can't needinfo users whose bugzilla email doesn't match their commit email

[jgraham]

We currently assume that all bugzilla emails match the commit email in the case we need to needinfo comitters to get some input on a bug. That sometimes fails. We could do better here e.g. try to pick an email address from the assignee of the bug, or manually curate a map of commit emails to bugzilla emails, filling it in from cases that fail.