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: I8f7d772d51c6407207cbc8d6a9eab30939eccfde
Related-Bug: #1637509
Partial-Bug: #1644629

tasks/swift_install.yml

@@ -99,6 +99,16 @@
   notify:
     - Restart swift services
 
+- name: CentOS remove python from path first
+  file:
+    path:  "{{ swift_bin | dirname }}/bin/python2.7"
+    state: "absent"
+  when:
+    - ansible_pkg_mgr == 'yum'
+    - not swift_pypy_enabled | bool
+    - not swift_developer_mode | bool
+    - swift_get_venv | changed or swift_venv_dir | changed
+
 - name: Update virtualenv path
   command: >
     virtualenv-tools --update-path=auto --reinitialize {{ swift_bin | dirname }}