Fixups for problems discovered while testing for DTLS 1.3

[anhu]

The problems were found with the following configurations:

./configure --enable-dtls --enable-dtls13 CFLAGS="-DNO_WOLFSSL_CLIENT"
./configure --enable-dtls --enable-dtls13 CFLAGS="-DNO_WOLFSSL_SERVER"
./configure --enable-tls13 --disable-oldtls --enable-static --enable-singlethreaded --enable-dtls --enable-dtls13 --enable-sp=yes,4096 --disable-shared --enable-dtls-mtu --disable-sha3 --disable-dh --enable-curve25519 --enable-secure-renegotiation C_EXTRA_FLAGS="-DWOLFSSL_DTLS_ALLOW_FUTURE -DWOLFSSL_MIN_RSA_BITS=2048 -DWOLFSSL_MIN_ECC_BITS=256 -DFP_MAX_BITS=8192 -fomit-frame-pointer"

[dgarske]

@anhu please add here what build settings you used to reproduce and make some suggestions for new PRB test cases. Seems like we are missing some CI build test cases.

[anhu]

I've been assigned the task of creating new PRB tests for DTLS 1.3 and in the process of creating those tests, I've found these problems. Most of them came from these:

./configure --enable-dtls --enable-dtls13 CFLAGS="-DNO_WOLFSSL_CLIENT"

./configure --enable-dtls --enable-dtls13 CFLAGS="-DNO_WOLFSSL_SERVER"

I've tried about 20 different combinations so far. Can't remember which other ones were broken. I think there was only one more.

[anhu]

I didn't exactly know what to do here so I put todo... Is fallthrough alright? If so, I can change to fallthrough.
Let me know please.

[dgarske]

Yes this is fine for the sniffer. Thanks