increase 1-second timeout in fetchlimit

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.

(cherry picked from commit 45f330339c640dc0c27101942a2a107fa1972dd4)