Honour single read per client isc_nm_read() call in the TLSDNS [v9.18]
NOTE: This change was reverted in !7349 (merged).
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.
(cherry picked from commit e3c628d5) (backported from !7152 (merged))
Edited by Michał Kępień