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: I2d4d7c042c565984f3ead21e68d16e23e4c286b6
Related-Bug: #1637509
Partial-Bug: #1644629

tasks/tempest_install.yml

@@ -107,6 +107,15 @@
   delay: 2
   when: tempest_developer_mode | bool
 
+- name: CentOS remove python from path first
+  file:
+    path:  "{{ tempest_venv_bin | dirname }}/bin/python2.7"
+    state: "absent"
+  when:
+    - ansible_pkg_mgr == 'yum'
+    - not tempest_developer_mode | bool
+    - tempest_get_venv | changed or tempest_venv_dir | changed
+
 - name: Update virtualenv path
   command: >
     virtualenv-tools --update-path=auto --reinitialize {{ tempest_venv_bin | dirname }}