Send the :links option to the file server

Previously, the server was never asked to follow links when 'links =>
follow' was used, so the server always provided the metadata for the
link itself. With this patch, the server correctly follows the link
server-side and the client can apply the catalog correctly.
(#7680) Update tests for changed behaviour after bugfix

A number of tests were broken before the bugfix:
* incorrectly checking the file mode (missing .should)
* operating on a non-existent source symlink

Enabled all of the #10315 tests which now pass, some of which needed
editing due to the expected behaviour now being different for
links => follow.
Update Puppet::FileServing::Metadata tests

Provide a stub for resource[:links] => :manage
Expect :find to be called with :links => :manage
(#7680) Add acceptance test for file links => follow
Merge branch 'pull-1529'

This closes GH-1529