Remove global log buffer feature entirely

A earlier commit changed the global log buffer so that it only
records messages that are explicitly requested via the log
filters setting. This removes the performance burden, and
improves the signal/noise ratio for messages in the global
buffer. At the same time though, it is somewhat pointless, since
all the recorded log messages are already going to be sent to an
explicit log output like syslog, stderr or the journal. The
global log buffer is thus just duplicating this data on stderr
upon crash.

The log_buffer_size config parameter is left in the augeas
lens to prevent breakage for users on upgrade. It is however
completely ignored hereafter.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

docs/logging.html.in

@@ -38,12 +38,6 @@
           all messages to a debugging file but only allow errors to be
           logged through syslog.</li>
     </ul>
-    <p>Note that the logging module saves all logs to a <b>debug buffer</b>
-       filled in a round-robin fashion as to keep a full log of the
-       recent logs including all debug. The debug buffer can be resized
-       or deactivated in the daemon using the log_buffer_size variable,
-       default is 64 kB. This can be used when debugging the library
-       (see the virLogBuffer variable content).</p>
 
     <h2>
       <a name="log_config">Configuring logging in the library</a>
@@ -245,9 +239,5 @@ log_outputs="1:file:/var/log/libvirt/libvirtd.log"</pre>
     <p>in libvirtd.conf and restart the daemon will allow to
     gather a copious amount of debugging traces for the operations done
     in those areas.</p>
-    <p>On the other hand to deactivate the logbuffer in the daemon
-    for stable high load servers, set</p>
-    <pre>log_buffer_size=0</pre>
-    <p>in the libvirtd.conf.</p>
   </body>
 </html>