This reverts commit f17f5e831b that made
following change:
> The TLSDNS transport was not honouring the single read callback for
> TLSDNS client. It would call the read callbacks repeatedly in case the
> single TLS read would result in multiple DNS messages in the decoded
> buffer.
Turns out that this change broke XoT, so we are reverting the change
until we figure out a proper fix that will keep the design promise and
not break XoT at the same time.
d0d9e7dfb2