lib/oeqa/utils/sshcontrol: correct condition for ending the select() loop

This was set backwards; per https://docs.python.org/3/library/subprocess.html#subprocess.Popen.returncode
a return code of None indicates the process is still running,
and so the code entered a busyloop that ended on timeout
5 minutes later, lengthening selftests significantly.

(From OE-Core rev: a6690deffd7ddbce0e784701ea3fdbb84313b009)

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/utils/sshcontrol.py

@@ -58,7 +58,7 @@ class SSHProcess(object):
                         data = os.read(self.process.stdout.fileno(), 1024)
                         if not data:
                             self.process.poll()
-                            if self.process.returncode is None:
+                            if self.process.returncode is not None:
                                 self.process.stdout.close()
                                 eof = True
                         else: