stop libraries being required multiple times

The previous use of require caused File.join on several occasions to
calculate different paths to the same library, depending on which
__FILE__ the library was being calculated as relative to; e.g.
/some/path/prefix/spec/one/bar.rb would do the equivalent of:

  require '/some/path/prefix/spec/one/../../libraries/foo/mylib.rb'

and /some/path/prefix/spec/two/baz.rb would do the equivalent of:

  require '/some/path/prefix/spec/two/../../libraries/foo/mylib.rb'

This would result in mylib.rb being loaded multiple times, causing
warnings from constants being redefined, and worse, multiple objects
representing the same class hierarchy (@@foo) variables.  The latter
actually broke the @@subclasses registration mechanism in
Pacemaker::CIBObject.

By switching to File.expand_path, we ensure we always refer to each
library using a single absolute path, which means Ruby's require
mechanism works as it should, only loading the code the first time
round.

providers/location.rb

@@ -17,8 +17,8 @@
 # limitations under the License.
 #
 
-require ::File.join(::File.dirname(__FILE__),
-                    *%w(.. libraries pacemaker cib_object))
+require ::File.expand_path('../libraries/pacemaker/cib_object',
+                           ::File.dirname(__FILE__))
 
 action :create do
   name = new_resource.name