Default use_stderr to False

While defaulting use_stderr to True might be a useful development
default, it is not useful for operators. Operators using systemd,
upstart, or any of these kinds of services, will find that if they
specify --log-file they will have two copies of the same logs on their
disk:

- one in the service log (e.g., /var/log/upstart)
- one in the log file they specify with --log-file

Instead of operators having to disable stderr log in every
configuration, we should just default it to False here.

Closes-bug #1588051

Change-Id: I85f8670d98d03101888fb7bb0c89eb809719b4e8

oslo_log/_options.py

@@ -98,7 +98,7 @@ logging_cli_opts = [
 
 generic_log_opts = [
     cfg.BoolOpt('use_stderr',
-                default=True,
+                default=False,
                 help='Log output to standard error. '
                      + _IGNORE_MESSAGE),
 ]

releasenotes/notes/use_stderr_default_false-50d846b88cf2be90.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - Configuration option `use_stderr`'s default value is
+    False now, this will avoid same logs on service log and
+    specific log file by option --log-file.