lei q: fix auth IMAP --output with remote mboxrd

lei q: fix auth IMAP --output with remote mboxrd

IMAP authentication info is only shared amongst lei2mail workers,
so we must ensure all IMAP writes go through lei2mail workers
even if we don't have to access the mail through git.

This allows us to decouple the latency of the remote mboxrd from
the latency of the IMAP --output at the expense of extra IPC
overhead within our own processes.