increase 1-second timeout in fetchlimit

when "checking lame server clients are dropped below the hard limit",
periodically a query is sent for a name for which the server is
authoritative, to verify that legitimate queries can still be
processed while the server is dealing with a flood of lame delegation
queries. those queries used the same dig options as elsewhere in the
fetchlimit test, including "+tries=1 +timeout=1". on slow systems, a
1-second timeout may be insufficient to get an answer even if the server
is behaving well. this commit increases the timeout for the check
queries to 2 seconds in hopes that will be enough to eliminate test
failures in CI.

bin/tests/system/fetchlimit/tests.sh

@@ -161,7 +161,7 @@ success=0
 touch ans4/norespond
 for try in 1 2 3 4 5; do
     burst b $try 400
-    $DIGCMD a ${try}.example > dig.out.ns3.$try
+    $DIGCMD +time=2 a ${try}.example > dig.out.ns3.$try
     stat 400 || exceeded=`expr $exceeded + 1`
     grep "status: NOERROR" dig.out.ns3.$try > /dev/null 2>&1 && \
             success=`expr $success + 1`