Skip ECDH ciphersuites for O->m pair

The mechanism of detecting unsupported ciphersuites
for OpenSSL client doesn't work on a modern OpenSSL.
At least, it fails on Travis CI which is installed
with OpenSSL 1.1.1f. So we need to skip ECDH cipher-
suites for O->m.

Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>

tests/compat.sh

@@ -1058,6 +1058,7 @@ for MODE in $MODES; do
                         start_server "mbedTLS"
                         translate_ciphers o $O_CIPHERS
                         for i in $ciphers; do
+                            o_check_ciphersuite "${i%%=*}"
                             run_client OpenSSL ${i%%=*} ${i#*=}
                         done
                         stop_server