Remove "error" allowance in dtls_server

Now that dtls_server doesn't print "error" when it receives stray messages
while it's waiting for a second handshake, have the tests fail if "error" is
printed for some other reason.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/opt-testcases/sample.sh b/tests/opt-testcases/sample.sh
index e2eaf24..88f3b12 100644
--- a/tests/opt-testcases/sample.sh
+++ b/tests/opt-testcases/sample.sh
@@ -334,11 +334,6 @@
             -S "error" \
             -C "ERROR"
 
-# The server complains of extra data after it closes the connection
-# because the client keeps sending data, so the server receives
-# more application data when it expects a new handshake. We consider
-# the test a success if both sides have sent and received application
-# data, no matter what happens afterwards.
 run_test    "Sample: dtls_client with dtls_server" \
             -P 4433 \
             "$PROGRAMS_DIR/dtls_server" \
@@ -348,13 +343,9 @@
             -s "[1-9][0-9]* bytes written" \
             -c "[1-9][0-9]* bytes read" \
             -c "[1-9][0-9]* bytes written" \
+            -S "error" \
             -C "error"
 
-# The server complains of extra data after it closes the connection
-# because the client keeps sending data, so the server receives
-# more application data when it expects a new handshake. We consider
-# the test a success if both sides have sent and received application
-# data, no matter what happens afterwards.
 run_test    "Sample: ssl_client2, dtls_server" \
             -P 4433 \
             "$PROGRAMS_DIR/dtls_server" \
@@ -364,6 +355,7 @@
             -s "[1-9][0-9]* bytes written" \
             -c "[1-9][0-9]* bytes read" \
             -c "[1-9][0-9]* bytes written" \
+            -S "error" \
             -C "error"
 
 requires_protocol_version dtls12