Fix two issues with AES-CCM KTLS tests.

Fix two issues with AES-CCM KTLS tests.

- Apply the cipher list to the server context as well as the client
  context.  The tests still worked for AES-GCM cipher suites as those
  are in the default list of ciphers.  AES-CCM cipher suites are not
  in the default list and require the cipher list to be set.

- Use the correct cipher name for AES-CCM.

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/12111)