Adding os realpath filter.

This is particularly useful when wanting to get the absolute path of filepaths found by the 'fileglob' filter.
This also lets you provide absolute paths to roles, which search for files in different areas unless absolutely pathed.

lib/ansible/runner/filter_plugins/core.py

@@ -120,6 +120,7 @@ class FilterModule(object):
             # path
             'basename': os.path.basename,
             'dirname': os.path.dirname,
+            'realpath': os.path.realpath,
 
             # failure testing
             'failed'  : failed,