Simplify pip install options

Using the omit template, we can now better control which pip options
we set.

Change-Id: I182dec217f88da846488e497b062920e2a72a2d9
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

defaults/main.yaml

@@ -60,7 +60,9 @@ nodepool_git_version: master
 nodepool_install_method: git
 
 nodepool_pip_name: nodepool
-nodepool_pip_version:
+#nodepool_pip_extra_args:
+#nodepool_pip_version:
+#nodepool_pip_virtualenv:
 
 # tasks/service.yaml
 nodepool_file_nodepool_service_group: root

tasks/install/git.yaml

@@ -20,4 +20,6 @@
 
 - name: Pip install nodepool from local git repo.
   pip:
+    extra_args: "{{ nodepool_pip_extra_args|default(omit) }}"
     name: "file://{{ nodepool_git_dest }}"
+    virtualenv: "{{ nodepool_pip_virtualenv|default(omit) }}"

tasks/install/pip.yaml

@@ -14,11 +14,7 @@
 ---
 - name: Install nodepool using pip.
   pip:
+    extra_args: "{{ nodepool_pip_extra_args|default(omit) }}"
     name: "{{ nodepool_pip_name }}"
-  when: nodepool_pip_version is none
-
-- name: Install nodepool using pip.
-  pip:
-    name: "{{ nodepool_pip_name }}"
-    version: "{{ nodepool_pip_version }}"
-  when: nodepool_pip_version is not none
+    version: "{{ nodepool_pip_version|default(omit) }}"
+    virtualenv: "{{ nodepool_pip_virtualenv|default(omit) }}"