Optimise pip install tasks

Unlike the Ansible apt module, the Ansible pip module does not
recognise a with_items list and process all the items at once.

To optimise the pip install tasks, this patch replaces the use
of with_items with a join filter so that the pip install task
does an install with all the packages in a list, ensuring that
the execution is one action instead of many.

Change-Id: I590de35eb92623f1c280a31db492e1b23726b3f9

tasks/tempest_install.yml

@@ -59,14 +59,13 @@
 
 - name: Install requires pip packages
   pip:
-    name: "{{ item }}"
+    name: "{{ tempest_requires_pip_packages | join(' ') }}"
     state: latest
     extra_args: "{{ pip_install_options_fact }}"
   register: install_packages
   until: install_packages|success
   retries: 5
   delay: 2
-  with_items: "{{ tempest_requires_pip_packages }}"
   tags:
     - tempest-install
     - tempest-pip-packages
@@ -191,7 +190,7 @@
 
 - name: Install pip packages (venv)
   pip:
-    name: "{{ item }}"
+    name: "{{ tempest_pip_packages | join(' ') }}"
     state: latest
     virtualenv: "{{ tempest_venv_bin | dirname }}"
     virtualenv_site_packages: "no"
@@ -200,7 +199,6 @@
   until: install_packages|success
   retries: 5
   delay: 2
-  with_items: "{{ tempest_pip_packages }}"
   when:
     - tempest_venv_enabled | bool
     - tempest_get_venv | failed or tempest_developer_mode | bool
@@ -210,14 +208,13 @@
 
 - name: Install pip packages (no venv)
   pip:
-    name: "{{ item }}"
+    name: "{{ tempest_pip_packages | join(' ') }}"
     state: latest
     extra_args: "{{ pip_install_options_fact }}"
   register: install_packages
   until: install_packages|success
   retries: 5
   delay: 2
-  with_items: "{{ tempest_pip_packages }}"
   when:
     - not tempest_venv_enabled | bool
     - not tempest_developer_mode | bool