Increase timeout delays in new timeouts isolation test.

Buildfarm member friarbird doesn't like this test as-committed, evidently
because it's so slow that the test framework doesn't reliably notice that
the backend is waiting before the timeout goes off.  (This is not totally
surprising, since friarbird builds with -DCLOBBER_CACHE_ALWAYS.)  Increase
the timeout delay from 1 second to 2 in hopes of resolving that problem.