Run the dnssec system tests with set -e enabled

bin/tests/system/dnssec/ns6/sign.sh

@@ -12,6 +12,8 @@
 # shellcheck source=conf.sh
 . "$SYSTEMTESTTOP/conf.sh"
 
+set -e
+
 zone=optout-tld
 infile=optout-tld.db.in
 zonefile=optout-tld.db
@@ -20,4 +22,4 @@ keyname=$("$KEYGEN" -q -a "$DEFAULT_ALGORITHM" -b "$DEFAULT_BITS" -n zone "$zone
 
 cat "$infile" "$keyname.key" > "$zonefile"
 
-"$SIGNER" -P -3 - -A -o "$zone" "$zonefile" > /dev/null
+"$SIGNER" -P -3 - -A -o "$zone" "$zonefile" > /dev/null 2>&1