Increase rsyslog buffer sizes.

Swift proxy logs to syslog during the devstack-gate tempest runs. To
better capture the swift logs increase the rsyslog buffer size to 6k
bytes allowing for longer messages like tracebacks.

Change-Id: I03e42964e14d9f930c07ed047851bdf775639c59

modules/jenkins/manifests/slave.pp

@@ -338,7 +338,20 @@ class jenkins::slave(
     }
   }
 
+  # Increase syslog message size in order to capture
+  # python tracebacks with syslog.
   file { '/etc/rsyslog.d/99-maxsize.conf':
-    ensure => absent,
+    ensure  => present,
+    # Note MaxMessageSize is not a puppet variable.
+    content => '$MaxMessageSize 6k',
+    owner   => 'root',
+    group   => 'root',
+    mode    => '0644',
+  }
+
+  service { 'rsyslog':
+    ensure    => running,
+    enable    => true,
+    subscribe => File['/etc/rsyslog.d/99-maxsize.conf'],
   }
 }