Improve delete all job performance

delete-all command was deleting one job at a time using the jenkins
doDelete rest endpoint which is very slow.  Change Ia4fbfca970165
allows us to execute a groovy script on the jenkins server to
do the same thing.  The only difference is that running the script
on the server will delete all jobs much faster.

As a data point:
I added all (~5,000) openstack jobs to my jenkins server.
The previous delete_all took many hours to delete all the
jobs while the script method did it in a matter of seconds.

Change-Id: Id7f7dfb567997e042fe0f783e54680482fefdc15
depends-on: Ia4fbfca970165d890d7e076f47ddcde7633afa9b

jenkins_jobs/builder.py

@@ -142,6 +142,13 @@ class Jenkins(object):
             logger.info("Deleting jenkins job {0}".format(job_name))
             self.jenkins.delete_job(job_name)
 
+    def delete_all_jobs(self):
+        # execute a groovy script to delete all jobs is much faster than
+        # using the doDelete REST endpoint to delete one job at a time.
+        script = ('for(job in jenkins.model.Jenkins.theInstance.getProjects())'
+                  '       { job.delete(); }')
+        self.jenkins.run_script(script)
+
     def get_plugins_info(self):
         """ Return a list of plugin_info dicts, one for each plugin on the
         Jenkins instance.
@@ -275,8 +282,7 @@ class Builder(object):
     def delete_all_jobs(self):
         jobs = self.jenkins.get_jobs()
         logger.info("Number of jobs to delete:  %d", len(jobs))
-        for job in jobs:
-            self.delete_job(job['name'])
+        self.jenkins.delete_all_jobs()
 
     def update_job(self, input_fn, jobs_glob=None, output=None):
         self.load_files(input_fn)

requirements.txt

@@ -2,5 +2,5 @@ argparse
 ordereddict
 six>=1.5.2
 PyYAML
-python-jenkins>=0.4.1
+python-jenkins>=0.4.8
 pbr>=0.8.2,<2.0