Merge pull request #3088 from edx/jibsheet/install-psmisc

psmisc isn't on precise docker images and the jenkins roles want it.

playbooks/roles/jenkins_master/defaults/main.yml

@@ -100,6 +100,7 @@ jenkins_debian_pkgs:
     - maven
     - daemon
     - python-pycurl
+    - psmisc
 
 # Extra packages need for a specific jenkins instance.
 JENKINS_EXTRA_PKGS: []