Fix DTLS failure when used in a build which has SCTP enabled

The value of BIO_CTRL_DGRAM_SET_PEEK_MODE was clashing with the value for
BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE. In an SCTP enabled build
BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE was used unconditionally with
the reasoning that it would be ignored if SCTP wasn't in use. Unfortunately
due to this clash, this wasn't the case. The BIO ended up going into peek
mode and was continually reading the same data over and over - throwing it
away as a replay.

Fixes #3723

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3724)

ssl/statem/statem.c

diff --git a/ssl/statem/statem.c b/ssl/statem/statem.c
index 52beac7..9eab8ce 100644
--- a/ssl/statem/statem.c
+++ b/ssl/statem/statem.c
@@ -300,10 +300,10 @@
             return -1;
     }
 #ifndef OPENSSL_NO_SCTP
-    if (SSL_IS_DTLS(s)) {
+    if (SSL_IS_DTLS(s) && BIO_dgram_is_sctp(SSL_get_wbio(s))) {
         /*
          * Notify SCTP BIO socket to enter handshake mode and prevent stream
-         * identifier other than 0. Will be ignored if no SCTP is used.
+         * identifier other than 0.
          */
         BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
                  st->in_handshake, NULL);
@@ -421,10 +421,10 @@
     st->in_handshake--;
 
 #ifndef OPENSSL_NO_SCTP
-    if (SSL_IS_DTLS(s)) {
+    if (SSL_IS_DTLS(s) && BIO_dgram_is_sctp(SSL_get_wbio(s))) {
         /*
          * Notify SCTP BIO socket to leave handshake mode and allow stream
-         * identifier other than 0. Will be ignored if no SCTP is used.
+         * identifier other than 0.
          */
         BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE,
                  st->in_handshake, NULL);