FIXED: CLP(ℤ): Correctly remove all attributes during propagation of all_distinct...

FIXED: CLP(ℤ): Correctly remove all attributes during propagation of all_distinct/1 and other global constraints.

The constraints from library(clpz) were already correctly removed, but
others such as pending freeze/2 goals were not, potentially leading to
an accumulation of redundant constraints during propagation.

Test case:

   ?- freeze(A,(X=1;X=2)), all_distinct([A]), A = 1.
      A = 1, X = 1
   ;  A = 1, X = 2.

The combination of freeze/2 and CLP(ℤ) is useful for example when
creating animations of search processes.

This addresses #1624.