Cyril Brulebois authored Jan 10, 2019 and intrigeri committed Apr 14, 2019

IO.popen makes it possible to start a command as a child process but it
won't automatically reap the subprocess when it exits, leading to many
zombies when running the automated test suite.

Fix this in several ways depending on the call site:

 * Create an intermediary variable to hold the subprocess returned by
   IO.popen, making it possible to read its standard output, but also
   allowing to call its close method afterwards. This is less
   straightforward than a IO.popen().gets call, but allows for
   appropriate clean-up.

 * When the subprocess object itself (p) is available, add a "p.close"
   call after killing it through "Process.kill(signal, p.pid)".

 * Otherwise, when only the pid of the subprocess is available, call
   "Process.wait(pid)" after killing it.