Upgrade gnutls-next to 3.7.2

v3.7.2 introduces DISABLE_TLS13_COMPAT_MODE. That can be
used to verify if TLS13 COMPATIBLE is not available.

Change-Id: Id68748e92504835b5a63b2565a618f728e7222f6
Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/tests/ssl-opt-in-docker.sh b/tests/ssl-opt-in-docker.sh
index 401a69c..e7bb01d 100755
--- a/tests/ssl-opt-in-docker.sh
+++ b/tests/ssl-opt-in-docker.sh
@@ -42,13 +42,13 @@
 
 case "${GNUTLS_CLI:-default}" in
     "legacy")  export GNUTLS_CLI="/usr/local/gnutls-3.3.8/bin/gnutls-cli";;
-    "next")  export GNUTLS_CLI="/usr/local/gnutls-3.6.5/bin/gnutls-cli";;
+    "next")  export GNUTLS_CLI="/usr/local/gnutls-3.7.2/bin/gnutls-cli";;
     *) ;;
 esac
 
 case "${GNUTLS_SERV:-default}" in
     "legacy")  export GNUTLS_SERV="/usr/local/gnutls-3.3.8/bin/gnutls-serv";;
-    "next")  export GNUTLS_SERV="/usr/local/gnutls-3.6.5/bin/gnutls-serv";;
+    "next")  export GNUTLS_SERV="/usr/local/gnutls-3.7.2/bin/gnutls-serv";;
     *) ;;
 esac