oeqa/qemurunner: do not use Popen.poll() when terminating runqemu with a signal

This does not actually guarantee that the child runqemu process has completely exited:
poll() may return prematurely while the SIGTERM handler in runqemu is still running.
This thwarts the rest of the processing, and may terminate the handler before
it completes.

Use Popen.communicate() instead: this is what python documentation recommends as well:
https://docs.python.org/3/library/subprocess.html#subprocess.Popen.communicate

(From OE-Core rev: 3793662bcfdab230d7b98bde2bc6757949b0aca0)

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit cd3e55606c427287f37585c5d7cde936471e52f4)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/utils/qemurunner.py

@@ -432,10 +432,13 @@ class QemuRunner:
                 except OSError as e:
                     if e.errno != errno.ESRCH:
                         raise
-            endtime = time.time() + self.runqemutime
-            while self.runqemu.poll() is None and time.time() < endtime:
-                time.sleep(1)
-            if self.runqemu.poll() is None:
+            try:
+                outs, errs = self.runqemu.communicate(timeout = self.runqemutime)
+                if outs:
+                    self.logger.info("Output from runqemu:\n%s", outs.decode("utf-8"))
+                if errs:
+                    self.logger.info("Stderr from runqemu:\n%s", errs.decode("utf-8"))
+            except TimeoutExpired:
                 self.logger.debug("Sending SIGKILL to runqemu")
                 os.killpg(os.getpgid(self.runqemu.pid), signal.SIGKILL)
             if not self.runqemu.stdout.closed: