sandbox: tests - close stdout of p1

p1.stdout should be closed after it's connected to p2 according to
https://docs.python.org/3/library/subprocess.html#replacing-shell-pipeline

Fixes:
$ make PYTHON=python3 test
Verify that we can read file descriptors handed to sandbox ...
/usr/lib64/python3.5/unittest/case.py:638: ResourceWarning: unclosed
file <_io.BufferedReader name=4>
  testMethod()

Signed-off-by: Petr Lautrbach <plautrba@redhat.com>
1 file changed