Don't close file descriptors when starting python program

Python programs run via a wrapper script. That wrapper script
can be started with open file descriptors, for example by using
the <(echo foo) syntax in bash. The shouldn't be closed when
starting the real script.

Bug: 203436762
Test: Presubmits
Change-Id: Ib20450f713b15c8a5527d1e433bfd9635cead85f