Bug 835149 - [email/IMAP] folder list sync breaks if IMAP server (ex: courier) returns folders in non-hierarchy order. r=squib

https://bugzilla.mozilla.org/show_bug.cgi?id=835149
land GELAM PR that has r=squib:
https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/117