Add optional parameter to set JJB version from PIP

Allow set version constraint when installing JJB using PIP, like

parameters:
  jenkins:
    job_builder:
      source:
        engine: git
        version: '>=1.6.0,<2.0.0'
...

i.e. version string is just added to the package name:

  jenkins-job-builder>=1.6.0,<2.0.0

Change-Id: I5e295ab25a19dd61a3fa40b36a69f75d2d0053f9
diff --git a/jenkins/job_builder.sls b/jenkins/job_builder.sls
index 01c5238..c13cecd 100644
--- a/jenkins/job_builder.sls
+++ b/jenkins/job_builder.sls
@@ -25,7 +25,7 @@
 jenkins_job_builder_install:
   pip.installed:
   - names:
-    - jenkins-job-builder
+    - 'jenkins-job-builder{{ job_builder.source.version|default("") }}'
   - require:
     - pkg: jenkins_job_builder_packages
   - require_in: