Emit deprecated warning for K* file pairs

We try reading the same file using different methods so only
emit a warning if we successfully read the file.

bin/tests/system/nsupdate/tests.sh

@@ -1022,7 +1022,7 @@ else
 	echo_i "skipping disabled md5 (157) algorithm"
 fi
 for alg in $ALGS; do
-    $NSUPDATE -k ns1/legacy/Klegacy-${alg}.+${alg}+*.key <<END > /dev/null || ret=1
+    $NSUPDATE -k ns1/legacy/Klegacy-${alg}.+${alg}+*.key <<END > nsupdate.alg-$alg.out 2>&1 || ret=1
 server 10.53.0.1 ${PORT}
 update add ${alg}.keytests.nil. 600 A 10.10.10.3
 send
@@ -1031,6 +1031,7 @@ done
 sleep 2
 for alg in $ALGS; do
     $DIG $DIGOPTS +short @10.53.0.1 ${alg}.keytests.nil | grep 10.10.10.3 > /dev/null 2>&1 || ret=1
+    grep "Use of K\* file pairs for HMAC is deprecated" nsupdate.alg-$alg.out > /dev/null || ret=1
 done
 if [ $ret -ne 0 ]; then
     echo_i "failed"