Issue introduced by OpenSSL 1.1.1c causes valgrind errors to be reported. See
https://www.mail-archive.com/openssl-commits@openssl.org/msg21701.html and
https://github.com/openssl/openssl/pull/8606 which did not make 1.1.1c
scripts/build.sh:
tests/valgrind_suppression:
Temporarily suppress valgrind errors when SSL_CTS_new() is called when running
the tests.
Note: This suppression will also need to be applied when running valgrind
against other CoAP executables using OpenSSL 1.1.1c to prevent the valgrind
errors getting reported.
src/coap_openssl.c:
memset cookie_secret to 0 to stop valgrind warning.
