tools/jenkins-jobs-builder: Workaround jenkins-job 6.2.0 regression

Latest release of jenkins-job-builder is now attempting to delete old
Jenkins views when updating but this new code triggers an exception when
deploying jobs on our Jenkins instance, so add option --jobs-only to
jenkins-job update command as a workaround to restore previous behavior.

README.md

@@ -38,7 +38,7 @@ Connect to localhost:8080, then within the jenkins ui:
     ...)
   - Add a `build` step `Execute shell` with this content
 ```
-tox -- update --delete-old
+tox -- update --delete-old --jobs-only
 ```
 - Save your build configuration
 - Trigger a build \o/

docker/create_swh_jobs.groovy

@@ -36,7 +36,7 @@ def jobXml = '''<?xml version='1.1' encoding='UTF-8'?>
   <concurrentBuild>false</concurrentBuild>
   <builders>
     <hudson.tasks.Shell>
-      <command>tox -- update --delete-old</command>
+      <command>tox -- update --delete-old --jobs-only</command>
       <configuredLocalRules/>
     </hudson.tasks.Shell>
   </builders>

jobs/tools/jenkins-jobs-builder.groovy.j2

@@ -44,7 +44,7 @@ pipeline {
       }
       steps {
         script {
-          sh('tox -- update --delete-old')
+          sh('tox -- update --delete-old --jobs-only')
           build(
             job: '/jenkins-tools/setup-gitlab-webhooks'
           )