Increase some test sleeps

SBCL is terribly slow at spawning new processes on Linux when the maximum
number of file descriptors is large. See
https://sourceforge.net/p/sbcl/mailman/sbcl-devel/thread/CAF63%3D11qTxqDVDm5ZL6T1yrkcaAnk7%2BCwQgX3xDAtqx5Q9fNjQ%40mail.gmail.com/#msg37013559

Docker environments (like the gitlab.common-lisp.net CI ruuners) tend to
default to setting a very high max_fd and are likely affected by this and can
throw off timing for run-program tests. "Fix" for the time being by increasing
how long the processes in this test sleep.
7 jobs for ci-tweaks in 21 minutes and 31 seconds (queued for 3 seconds)