Fix virtualenv-tools issue

please see fireteam/virtualenv-tools#5

This make installation of the virtualenv impossible on CentOS7 since
you endup with python > python2.7 and python2.7 > python

lrwxrwxrwx. 1 root root       9 Nov 24 20:49 python -> python2.7
lrwxrwxrwx. 1 root root       6 Nov 14 20:03 python2 -> python
lrwxrwxrwx. 1 root root       6 Nov 14 20:03 python2.7 -> python

Change-Id: I101fe7082cac887dc4299a0f5ec92bdce626bb79
Related-Bug: #1637509
Partial-Bug: #1644629

tasks/ceilometer_install.yml

@@ -89,6 +89,15 @@
   when: ceilometer_developer_mode | bool
   notify: Restart ceilometer services
 
+- name: CentOS remove python from path first
+  file:
+    path:  "{{ ceilometer_bin | dirname }}/bin/python2.7"
+    state: "absent"
+  when:
+    - ansible_pkg_mgr == 'yum'
+    - not ceilometer_developer_mode | bool
+    - ceilometer_get_venv | changed or ceilometer_venv_dir | changed
+
 - name: Update virtualenv path
   command: >
     virtualenv-tools --update-path=auto --reinitialize {{ ceilometer_bin | dirname }}