Use test random file for tsig test using keygen

This is for #42565: tsig test hangs and KEYGEN and randomdev

It was okayed there and is a trivial fix. No changes log needed.

bin/tests/system/tsig/setup.sh

@@ -14,4 +14,9 @@
 # OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 # PERFORMANCE OF THIS SOFTWARE.
 
+SYSTEMTESTTOP=..
+. $SYSTEMTESTTOP/conf.sh
+
 sh clean.sh
+
+test -r $RANDFILE || $GENRANDOM 400 $RANDFILE

bin/tests/system/tsig/tests.sh

@@ -236,9 +236,9 @@ fi
 
 echo "I:check that multiple dnssec-keygen calls don't emit dns_dnssec_findmatchingkeys warning"
 ret=0
-$KEYGEN -a hmac-sha256 -b 128 -n host example.net > keygen.out1 2>&1 || ret=1
+$KEYGEN -r $RANDFILE -a hmac-sha256 -b 128 -n host example.net > keygen.out1 2>&1 || ret=1
 grep dns_dnssec_findmatchingkeys keygen.out1 > /dev/null && ret=1
-$KEYGEN -a hmac-sha256 -b 128 -n host example.net > keygen.out2 2>&1 || ret=1
+$KEYGEN -r $RANDFILE -a hmac-sha256 -b 128 -n host example.net > keygen.out2 2>&1 || ret=1
 grep dns_dnssec_findmatchingkeys keygen.out2 > /dev/null && ret=1
 if [ $ret -eq 1 ] ; then
 	echo "I: failed"; status=1