digital_ocean.script(): rename local var to avoid shadowing

************* Module salt.cloud.clouds.digital_ocean
salt/cloud/clouds/digital_ocean.py:520: [W0621(redefined-outer-name), script] Redefining name 'script' from outer scope (line 516)
Merge pull request #9549 from cvrebert/patch-3

digital_ocean.script(): rename local var to avoid shadowing