provide default 'output' setting to log to /var/log/cloud-init-output.log

This has been "best practice" for quite some time, and its a common
request of "where is the output of my user-data programs".

http://askubuntu.com/questions/345344/where-are-the-logs-for-my-user-data-script-cloud-init

ChangeLog

@@ -9,6 +9,8 @@
    (LP: #1260072).
  - Azure: minor changes in logging output. ensure filenames are strings (not
    unicode).
+ - config/cloud.cfg.d/05_logging.cfg: provide a default 'output' setting, to
+   redirect cloud-init stderr and stdout /var/log/cloud-init-output.log.
 0.7.4:
  - fix issue mounting 'ephemeral0' if ephemeral0 was an alias for a
    partitioned block device with target filesystem on ephemeral0.1.

config/cloud.cfg.d/05_logging.cfg

@@ -59,3 +59,8 @@ log_cfgs:
  - [ *log_base, *log_file ]
 # A file path can also be used
 # - /etc/log.conf
+
+# this tells cloud-init to redirect its stdout and stderr to
+# 'tee -a /var/log/cloud-init-output.log' so the user can see output
+# there without needing to look on the console.
+output: {all: '| tee -a /var/log/cloud-init-output.log'}