Fix 'dict' object has no attribute split
Fix 'dict' object has no attribute split

After updating to 2015.5.5 the state calls of win_path.exists suddenly were broken due to the change in the reg.py module.
This commit fixes the win_path.exists read_key implementation to fit the reg.read_value implementation that was discussed in https://github.com/saltstack/salt/issues/25618
saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt