DCD-386: Use sync rather than install to use locked package versions.

bin/install-ansible

@@ -12,4 +12,4 @@ set -e
 
 pip install pipenv
 
-pipenv install
+pipenv sync

bin/run-all-tests

@@ -3,7 +3,7 @@
 set -e
 
 # Use Ansible from virtualenv if provided
-pipenv install molecule docker six
+pipenv sync --dev
 
 for role in `find roles/ -name molecule | sort`; do
     pushd `dirname $role`