set_is_unit_test/2 will now correctly set options.

* Previously, set_is_unit_test/2 would only process the argument 'false'
  and leave options it sets unchanged. This was mainly a problem on
  windows where the option 'load' was left to 'show', causing the entire
  Metta $corelib to be echoed to the terminal while loading it to
  memory. The present commit fixes that.
* Part of oingoing work to address trueagi-io#227.

prolog/metta_lang/metta_interp.pl

@@ -588,6 +588,13 @@
 'is-symbol'(X):- symbol(X).
 %:- (is_mettalog->switch_to_mettalog;switch_to_mettarust).
 
+set_is_unit_test(false):-
+  forall(option_value_def(A,B),set_option_value_interp(A,B)),
+  set_option_value_interp('trace-on-test',false),
+  set_option_value_interp('trace-on-fail',false),
+  set_option_value_interp('load',silent),
+  set_option_value_interp('test',false),
+  !.
 set_is_unit_test(TF):-
   forall(option_value_def(A,B),set_option_value_interp(A,B)),
   set_option_value_interp('trace-on-test',false),
@@ -600,6 +607,7 @@
   set_option_value_interp('trace-on-exec',TF),
   set_option_value_interp('trace-on-eval',TF),*/
  % if_t( \+ TF , set_prolog_flag(debug_on_interrupt,true)),
+ % TODO: what is this cutting here?
   !.
 
 :- meta_predicate fake_notrace(0).