Bump JJB pin to 1.6.2

In order to address a dependency installation issue around PBR
version capping, update to the stable point release of
jenkins-job-builder which solves that problem.

Change-Id: I999e9490217ef3f03cee46b7843fedf53230d230

manifests/launcher.pp

@@ -52,7 +52,7 @@ class zuul::launcher (
   }
 
   package { 'jenkins-job-builder':
-    ensure   => '1.6.1',
+    ensure   => '1.6.2',
     provider => openstack_pip,
     require  => Class['pip'],
   }