Discard a dead option

Old inactive inherited code, a code relic for sure.
Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1301)

apps/s_server.c

@@ -151,7 +151,7 @@ static const char *session_id_prefix = NULL;
 #ifndef OPENSSL_NO_DTLS
 static int enable_timeouts = 0;
 static long socket_mtu;
-static int cert_chain = 0;
+
 #endif
 static int dtlslisten = 0;
 
@@ -713,7 +713,7 @@ typedef enum OPTION_choice {
     OPT_SRPUSERSEED, OPT_REV, OPT_WWW, OPT_UPPER_WWW, OPT_HTTP, OPT_ASYNC,
     OPT_SSL_CONFIG, OPT_SPLIT_SEND_FRAG, OPT_MAX_PIPELINES, OPT_READ_BUF,
     OPT_SSL3, OPT_TLS1_2, OPT_TLS1_1, OPT_TLS1, OPT_DTLS, OPT_DTLS1,
-    OPT_DTLS1_2, OPT_TIMEOUT, OPT_MTU, OPT_CHAIN, OPT_LISTEN,
+    OPT_DTLS1_2, OPT_TIMEOUT, OPT_MTU, OPT_LISTEN,
     OPT_ID_PREFIX, OPT_RAND, OPT_SERVERNAME, OPT_SERVERNAME_FATAL,
     OPT_CERT2, OPT_KEY2, OPT_NEXTPROTONEG, OPT_ALPN,
     OPT_SRTP_PROFILES, OPT_KEYMATEXPORT, OPT_KEYMATEXPORTLEN,
@@ -881,7 +881,6 @@ OPTIONS s_server_options[] = {
     {"dtls", OPT_DTLS, '-', "Use any DTLS version"},
     {"timeout", OPT_TIMEOUT, '-', "Enable timeouts"},
     {"mtu", OPT_MTU, 'p', "Set link layer MTU"},
-    {"chain", OPT_CHAIN, '-', "Read a certificate chain"},
     {"listen", OPT_LISTEN, '-',
      "Listen for a DTLS ClientHello with a cookie and then connect"},
 #endif
@@ -1383,11 +1382,6 @@ int s_server_main(int argc, char *argv[])
         case OPT_MTU:
 #ifndef OPENSSL_NO_DTLS
             socket_mtu = atol(opt_arg());
-#endif
-            break;
-        case OPT_CHAIN:
-#ifndef OPENSSL_NO_DTLS
-            cert_chain = 1;
 #endif
             break;
         case OPT_LISTEN: