Refactor: libpacemaker: Split colocations_list into two functions.
    
    The point of this is to make it easier to follow along with what these
    functions do by eliminating some of the conditionals.  However, the
    names are confusing and probably can't be made much less confusing.
    
    * rscs_colocated_with_list outputs a list of all the resources that are
      colocated with the given resource argument.
    * rsc_is_colocated_with_list outputs a list of all the resources that
      the given resource argument is colocated with.