Fix Download get-pip play in vagrant.yml

Fixes syntax for get_url module in ansible playbook vagrant.yml
which was causing the vagrant up command to fail.

Change-Id: Iffb0b17c8f808b33538b06d21c52ca603f018a9c
Closes-Bug: 1521750

tools/vagrant_dev_env/vagrant.yml

@@ -20,8 +20,8 @@
       when: ansible_distribution == 'Ubuntu'
 
     - name: Download get-pip
-      get_url: https://bootstrap.pypa.io/get-pip.py
-      dest: /tmp/get-pip.py
+      get_url: url=https://bootstrap.pypa.io/get-pip.py
+               dest=/tmp/get-pip.py
 
     - name: Install pip
       shell: python /tmp/get-pip.py