DTLS: Do not call coap_session_disconnected_lkd() for writes

Let the upper calling layer do the coap_session_disconnected_lkd()
on detection of write error.

ChangeLog: Update with fixed CVEs

Release 4.3.5: Fix SO and ABI version for new release

release 4.3.5rc3: Release candidate 3 for 4.3.5

release 4.3.5rc2: Release candidate 2 for 4.3.5

RIOT: libcoap Release 4.3.5rc1

Bug fix update to 4.3.4a

pdu.c: Fix issue with 269 delta in internal coap_remove_option()

Update unit tests to check for a delta of 13 / 269.

Update version to release 4.3.3

RIOT: Update PKG_VERSION to point to 4.3.2 code