qemuzephyrrunner.py: use os._exit instead of sys.exit

sys.exit(0) can cause an error to be reported when the child exits, even
though not an error.  Since this is a child process, os._exit(0) is the
proper way to exit and not cause this issue.

Signed-off-by: Jon Mason <jon.mason@arm.com>
Signed-off-by: Naveen Saini <naveen.kumar.saini@intel.com>

lib/oeqa/utils/qemuzephyrrunner.py

@@ -191,7 +191,7 @@ class QemuZephyrRunner(QemuRunner):
             r = os.fdopen(r)
             x = r.read()
             os.killpg(os.getpgid(self.runqemu.pid), signal.SIGTERM)
-            sys.exit(0)
+            os._exit(0)
 
         bb.note("qemu started, pid is %s" % self.runqemu.pid)
         return self.create_socket()