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: I03baaa16662072a78f0d506c6d2b8e9c62f205f8

tasks/galera_client_install.yml

@@ -27,7 +27,7 @@
 
 - name: Install pip packages
   pip:
-    name: "{{ galera_client_pip_packages | join(' ') }}"
+    name: "{{ galera_client_pip_packages }}"
     state: "{{ galera_client_pip_package_state }}"
     extra_args: >-
       {{ (pip_install_upper_constraints is defined) | ternary('--constraint ' + pip_install_upper_constraints | default(''),'') }}