fix "read_only" setting in rsyncd setups

in all those places "true"/"false" are being used

also see I4d42f81cc3 where i wanted to remove
the quotes, but actually the rsync module says:

$read_only       - yes||no, defaults to yes

so i think where it says "true" it just happens
to work and where it says "false" it is still read-only?

either this, or the other way around, should the rsync
module start to use  true/false (but then as actual booleans)?

Change-Id: Ic91eb4f7c6817189b0a466a018c5544d65f8c02d