(QENG-713) add 'puppet_tmpdir' method

Add a 'puppet_tmpdir' method in Unix::File that creates temporary
directories which are owned by the puppet user.
(QENG-713) add test case and docs for 'puppet_tmpdir' method
(QENG-713) use DSL to access --configprint value
(QENG-713) Adds create_tmpdir_on DSL method.

Signed-off-by: Wayne <wayne@puppetlabs.com>
(QENG-713) Update to create_tmpdir_for_user, add spectests

Use `on` instead of `host.exec`.
Also removes test for Unix::Host.puppet_tmpdir.

Signed-off-by: Wayne <wayne@puppetlabs.com>
Merge pull request #302 from waynr/feature/create-tmpdir-for-user-on

Feature/create tmpdir for user on