Remove join filter from pip module tasks

Ansible 2.2 now treats the 'name' argument for the pip module
as a list, removing the need for us to implement the join
filter to optimise the install execution.

Change-Id: Id5d7d103c15711e4c9959112be46f777e06ded1d

tasks/almanach_install.yml

@@ -24,7 +24,7 @@
 
 - name: Install pip packages
   pip:
-    name: "{{ almanach_requires_pip_packages | join(' ') }}"
+    name: "{{ almanach_requires_pip_packages }}"
     state: present
     executable: pip3