Enable serialisation tests in ssl-opt.sh

They currently pass in a default build.
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index acbf414..c170df2 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -1322,56 +1322,50 @@
 
 # Tests for Context serialization
 
-skip_next_test
 requires_config_enabled MBEDTLS_SSL_CONTEXT_SERIALIZATION
-run_test    "(STUB) Context serialization, client serializes" \
-            "$P_SRV serialize=0 exchanges=2" \
-            "$P_CLI serialize=1 exchanges=2" \
+run_test    "Context serialization, client serializes" \
+            "$P_SRV dtls=1 serialize=0 exchanges=2" \
+            "$P_CLI dtls=1 serialize=1 exchanges=2" \
             0 \
             -c "Deserializing connection..." \
             -S "Deserializing connection..."
 
-skip_next_test
 requires_config_enabled MBEDTLS_SSL_CONTEXT_SERIALIZATION
-run_test    "(STUB) Context serialization, server serializes" \
-            "$P_SRV serialize=1 exchanges=2" \
-            "$P_CLI serialize=0 exchanges=2" \
+run_test    "Context serialization, server serializes" \
+            "$P_SRV dtls=1 serialize=1 exchanges=2" \
+            "$P_CLI dtls=1 serialize=0 exchanges=2" \
             0 \
             -C "Deserializing connection..." \
             -s "Deserializing connection..."
 
-skip_next_test
 requires_config_enabled MBEDTLS_SSL_CONTEXT_SERIALIZATION
-run_test    "(STUB) Context serialization, both serialize" \
-            "$P_SRV serialize=1 exchanges=2" \
-            "$P_CLI serialize=1 exchanges=2" \
+run_test    "Context serialization, both serialize" \
+            "$P_SRV dtls=1 serialize=1 exchanges=2" \
+            "$P_CLI dtls=1 serialize=1 exchanges=2" \
             0 \
             -c "Deserializing connection..." \
             -s "Deserializing connection..."
 
-skip_next_test
 requires_config_enabled MBEDTLS_SSL_CONTEXT_SERIALIZATION
-run_test    "(STUB) Context serialization, re-init, client serializes" \
-            "$P_SRV serialize=0 exchanges=2" \
-            "$P_CLI serialize=2 exchanges=2" \
+run_test    "Context serialization, re-init, client serializes" \
+            "$P_SRV dtls=1 serialize=0 exchanges=2" \
+            "$P_CLI dtls=1 serialize=2 exchanges=2" \
             0 \
             -c "Deserializing connection..." \
             -S "Deserializing connection..."
 
-skip_next_test
 requires_config_enabled MBEDTLS_SSL_CONTEXT_SERIALIZATION
-run_test    "(STUB) Context serialization, re-init, server serializes" \
-            "$P_SRV serialize=2 exchanges=2" \
-            "$P_CLI serialize=0 exchanges=2" \
+run_test    "Context serialization, re-init, server serializes" \
+            "$P_SRV dtls=1 serialize=2 exchanges=2" \
+            "$P_CLI dtls=1 serialize=0 exchanges=2" \
             0 \
             -C "Deserializing connection..." \
             -s "Deserializing connection..."
 
-skip_next_test
 requires_config_enabled MBEDTLS_SSL_CONTEXT_SERIALIZATION
-run_test    "(STUB) Context serialization, re-init, both serialize" \
-            "$P_SRV serialize=2 exchanges=2" \
-            "$P_CLI serialize=2 exchanges=2" \
+run_test    "Context serialization, re-init, both serialize" \
+            "$P_SRV dtls=1 serialize=2 exchanges=2" \
+            "$P_CLI dtls=1 serialize=2 exchanges=2" \
             0 \
             -c "Deserializing connection..." \
             -s "Deserializing connection..."