compat.sh: enable CBC-SHA-2 suites for GnuTLS

Recent GnuTLS packages on Ubuntu 16.04 have them disabled.

From /usr/share/doc/libgnutls30/changelog.Debian.gz:

gnutls28 (3.4.10-4ubuntu1.5) xenial-security; urgency=medium

  * SECURITY UPDATE: Lucky-13 issues
    [...]
    - debian/patches/CVE-2018-1084x-4.patch: hmac-sha384 and sha256
      ciphersuites were removed from defaults in lib/gnutls_priority.c,
      tests/priorities.c.

Since we do want to test the ciphersuites, explicitly re-enable them in the
server's priority string. (This is a no-op with versions of GnuTLS where those
are already enabled by default.)

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/compat.sh b/tests/compat.sh
index e0da373..b39a463 100755
--- a/tests/compat.sh
+++ b/tests/compat.sh
@@ -934,7 +934,7 @@
     M_SERVER_ARGS="server_port=$PORT server_addr=0.0.0.0 force_version=$MODE arc4=1"
     O_SERVER_ARGS="-accept $PORT -cipher NULL,ALL -$MODE -dhparam data_files/dhparams.pem"
     G_SERVER_ARGS="-p $PORT --http $G_MODE"
-    G_SERVER_PRIO="NORMAL:${G_PRIO_CCM}+ARCFOUR-128:+NULL:+MD5:+PSK:+DHE-PSK:+ECDHE-PSK:+RSA-PSK:-VERS-TLS-ALL:$G_PRIO_MODE"
+    G_SERVER_PRIO="NORMAL:${G_PRIO_CCM}+ARCFOUR-128:+NULL:+MD5:+PSK:+DHE-PSK:+ECDHE-PSK:+SHA256:+SHA384:+RSA-PSK:-VERS-TLS-ALL:$G_PRIO_MODE"
 
     # with OpenSSL 1.0.1h, -www, -WWW and -HTTP break DTLS handshakes
     if is_dtls "$MODE"; then