QUIC: fixed compat with ciphers other than AES128 (ticket #2500).

QUIC: fixed compat with ciphers other than AES128 (ticket #2500).

Previously, rec.level field was not uninitialized in SSL_provide_quic_data().
As a result, its value was always ssl_encryption_initial.  Later in
ngx_quic_ciphers() such level resulted in resetting the cipher to
TLS1_3_CK_AES_128_GCM_SHA256 and using AES128 to encrypt the packet.

Now the level is initialized and the right cipher is used.