Only replace python when re-initializing the venv

We reinitialize the venv to ensure that the right version of
python is in the venv, but we do not want virtualenv to also
replace pip, setuptools and wheel so we tell it not to. If we
don't do this then virtualenv will install the latest available
version, which is not what we want.

Change-Id: I6ee3814fdee1712fdbe82189495772f45ec9e684
Partial-Bug: #1764470

tasks/rally_install.yml

@@ -104,11 +104,22 @@
     - ansible_pkg_mgr == 'yum'
     - rally_get_venv | changed
 
-- name: Update virtualenv path
+# NOTE(odyssey4me):
+# We reinitialize the venv to ensure that the right
+# version of python is in the venv, but we do not
+# want virtualenv to also replace pip, setuptools
+# and wheel so we tell it not to.
+# We do not use --always-copy for CentOS/SuSE due
+# to https://github.com/pypa/virtualenv/issues/565
+- name: Reset virtualenv and update its paths
   shell: |
     find {{ rally_bin }} -name \*.pyc -delete
     sed -si '1s/^.*python.*$/#!{{ rally_bin | replace ('/','\/') }}\/python/' {{ rally_bin }}/*
-    virtualenv {{ rally_bin | dirname }}
+    virtualenv {{ rally_bin | dirname }} \
+        {{ (ansible_pkg_mgr == 'apt') | ternary('--always-copy', '') }} \
+        --no-pip \
+        --no-setuptools \
+        --no-wheel
   when: rally_get_venv | changed
   tags:
     - skip_ansible_lint