Fix problem with set_mode (chmod) behavior on different test environments.
Issuing a set_mode on a symlink with 0755 on MacOSX produces a link
with the correct mode. On other Linux's (Ubuntu, specifically) all
symlinks report 0777 regardless of how it was set. This mod simply
gets the mode after the symlink is created and uses that in the test
evaluation.
Reviewed by: josh@puppetlabs.com