Tests: unbreak quic_ciphers.t with AEAD_AES_128_CCM enabled. Although CCM ciphers are disabled in a stock OpenSSL as rarely used, "to reduce ClientHello bloat", AEAD_AES_128_CCM is apparently turned back in certain distributions such as RHEL. Previously, this caused testing connections to fail as the CCM cipher being negotiated isn't supported yet in nginx. Now the test is skipped instead on failure. While here, fixed nearby style.