In "ListNamespacePids", to check that a process is running inside a
namespace, a new thread is spawned. Inside it a shell command is
executed ("sleep <timeout>"). To avoid calling the method
"utils.kill_process" with the correspondent overhead when running as
root, this patch reduces the "sleep" time to a short period (3 seconds)
and lets the process to finish gracefully.
Trivial-Fix
Change-Id: Ib33e725b563b863810f61f457a0ddfee8edc5c2e