oeqa/utils/qemurunner: Fix python ResourceWarning for unclosed file

Fixes:

Stderr:
/media/build1/poky/meta/lib/oeqa/utils/qemurunner.py:381: ResourceWarning: unclosed file <_io.BufferedWriter name=16>
  self.runqemu = None

(From OE-Core rev: b9e0bf919e6fc1a58e02145a363ebe7066e5bf4f)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/utils/qemurunner.py

@@ -378,6 +378,8 @@ class QemuRunner:
             if self.runqemu.poll() is None:
                 self.logger.debug("Sending SIGKILL to runqemu")
                 os.killpg(os.getpgid(self.runqemu.pid), signal.SIGKILL)
+            self.runqemu.stdin.close()
+            self.runqemu.stdout.close()
             self.runqemu = None
         if hasattr(self, 'server_socket') and self.server_socket:
             self.server_socket.close()