folder: LocalStatus: revamp cachemessagelist()
folder: LocalStatus: revamp cachemessagelist()

- Do not redefine "file".
- break loop as soon as possible.

Signed-off-by: Nicolas Sebrecht <347709267ddd1958560c4c317ea3fd613f10a719@laposte.net>

frioux/offlineimap,frioux/offlineimap