Clean up developer mode logic

Fixes the ability to deploy a venv in cases where:
1) developer_mode is not enabled
2) A cached venv is not downloaded from the repo server

Additional cleanup to the developer_mode venv deployment
logic is implemented by adding a *_venv_download var
which is used to decouple developer_mode from the
cached venv extraction process so that a deployer
can force venv builds in-place (disable cached
venv usage) without enabling developer mode
constraints.

Change-Id: I6b0c6b4708b449e1961fce0e2b98389813844fc9

defaults/main.yml

@@ -33,6 +33,9 @@ tempest_developer_constraints:
 # Name of the virtual env to deploy into
 tempest_venv_tag: untagged
 tempest_venv_bin: "/openstack/venvs/tempest-{{ tempest_venv_tag }}/bin"
+# venv_download, even when true, will use the fallback method of building the
+# venv from scratch if the venv download fails.
+tempest_venv_download: "{{ not tempest_developer_mode | bool }}"
 tempest_venv_download_url: http://127.0.0.1/venvs/untagged/ubuntu/tempest.tgz
 
 # The location where the tempest logs will be placed

tasks/tempest_install.yml

@@ -48,7 +48,7 @@
     dest: "/var/cache/{{ tempest_venv_download_url | basename }}"
     checksum: "sha1:{{ lookup('url', tempest_venv_download_url | replace('tgz', 'checksum')) }}"
   register: tempest_get_venv
-  when: not tempest_developer_mode | bool
+  when: tempest_venv_download | bool
 
 - name: Remove existing venv
   file:
@@ -82,15 +82,14 @@
     state: directory
     mode: "0755"
   register: tempest_venv_dir
+  when: tempest_get_venv | changed
 
 - name: Unarchive pre-built venv
   unarchive:
     src: "/var/cache/{{ tempest_venv_download_url | basename }}"
     dest: "{{ tempest_venv_bin | dirname }}"
     copy: "no"
-  when:
-    - not tempest_developer_mode | bool
-    - tempest_get_venv | changed or tempest_venv_dir | changed
+  when: tempest_get_venv | changed
 
 - name: Install pip packages
   pip:
@@ -106,7 +105,7 @@
   until: install_packages|success
   retries: 5
   delay: 2
-  when: tempest_developer_mode | bool
+  when: tempest_get_venv | failed or tempest_get_venv | skipped
 
 - name: CentOS remove python from path first
   file:
@@ -114,15 +113,12 @@
     state: "absent"
   when:
     - ansible_pkg_mgr == 'yum'
-    - not tempest_developer_mode | bool
-    - tempest_get_venv | changed or tempest_venv_dir | changed
+    - tempest_get_venv | changed
 
 - name: Update virtualenv path
   command: >
     virtualenv-tools --update-path=auto --reinitialize {{ tempest_venv_bin | dirname }}
-  when:
-    - not tempest_developer_mode | bool
-    - tempest_get_venv | changed or tempest_venv_dir | changed
+  when: tempest_get_venv | changed
 
 - name: Get tempest plugins from git
   git: