consistently set and use Exec defaults

This should fix Errors like:

    Failed to apply catalog: Validation of
    Exec[mkdir_templates] failed: 'mkdir -p /opt/elasticsearch/config/templates_import' is not qualified and no path
    was specified. Please qualify the command or specify a path.

in a manner that is consistent across the code-base.
Merge pull request #47 from igalic/qualify_exec

consistently set and use Exec defaults