Add examples for 'predefined-parameters'

There was no example how to make multiline 'predefined-parameters'.

Change-Id: Ic287cd37ff928e34d80104085a3aca6f5d34865a
Closes-Bug: 1381079

tests/publishers/fixtures/trigger_parameterized_builds001.xml

@@ -6,7 +6,9 @@
       <hudson.plugins.parameterizedtrigger.BuildTriggerConfig>
         <configs>
           <hudson.plugins.parameterizedtrigger.PredefinedBuildParameters>
-            <properties>foo=bar</properties>
+            <properties>foo=bar
+bar=foo
+            </properties>
           </hudson.plugins.parameterizedtrigger.PredefinedBuildParameters>
         </configs>
         <projects>other_job, foo, bar</projects>

tests/publishers/fixtures/trigger_parameterized_builds001.yaml

@@ -1,7 +1,9 @@
 publishers:
   - trigger-parameterized-builds:
     - project: other_job, foo, bar
-      predefined-parameters: foo=bar
+      predefined-parameters: |
+        foo=bar
+        bar=foo
     - project: other_job1, other_job2
       predefined-parameters: BUILD_NUM=${BUILD_NUMBER}
       property-file: version.prop