green select: Delete unpatched poll once again
https://github.com/eventlet/eventlet/pull/317
Previously attempted in f63165c, had to be reverted in 8ea9df6 because
subprocess was failing after monkey patching.
Turns out we haven't been monkey patching the subprocess module at all,
this patch adds that in order for the tests to pass.
This part is changed because otherwise Popen class instantiation would
cause an infinite loop when monkey patching is applied:
-subprocess_orig = __import__("subprocess")
+subprocess_orig = patcher.original("subprocess")
This patch is contributed by Smarkets Limited.
* green subprocess: Provide green check_output
This patch is contributed by Smarkets Limited.