Bug 822882 - fix bisection on initial fetch. rs=squib

land https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/142
https://bugzilla.mozilla.org/show_bug.cgi?id=822882#c11
Merge pull request #8538 from asutherland/email-initial-bisect-fix

Bug 822882 - fix bisection on initial fetch. rs=squib