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: I12ee579625ee6ba493b970601b62f14614ce8658

tasks/glance_install.yml

@@ -51,14 +51,13 @@
 
 - name: Install requires pip packages
   pip:
-    name: "{{ item }}"
+    name: "{{ glance_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: "{{ glance_requires_pip_packages }}"
 
 - name: Get local venv checksum
   stat:
@@ -123,7 +122,7 @@
 
 - name: Install pip packages
   pip:
-    name: "{{ item }}"
+    name: "{{ glance_pip_packages | join(' ') }}"
     state: latest
     virtualenv: "{{ glance_bin | dirname }}"
     virtualenv_site_packages: "no"
@@ -132,7 +131,6 @@
   until: install_packages|success
   retries: 5
   delay: 2
-  with_items: "{{ glance_pip_packages }}"
   when:
     - glance_get_venv | failed or glance_developer_mode | bool
   notify: