memLeak analysis is affected by `__goblint_check`

[sim642]

@karoliineh found that our SV-COMP valid-memsafety verdict is impacted by inserting a __goblint_check into the program.
That is supposed to not impact the analysis at all (only output), so this behavior is wrong.

The offending code is here:

analyzer/src/analyses/memLeak.ml

Lines 230 to 245 in 153ce28

	| Assert { exp; _ } ->
	begin match man.ask (Queries.EvalInt exp) with
	| a when Queries.ID.is_bot a -> M.warn ~category:Assert "assert expression %a is bottom" d_exp exp
	| a ->
	begin match Queries.ID.to_bool a with
	| Some true -> ()
	| Some false ->
	(* If we know for sure that the expression in "assert" is false => need to check for memory leaks *)
	warn_for_multi_threaded_due_to_abort man;
	check_for_mem_leak man
	| None ->
	warn_for_multi_threaded_due_to_abort man;
	check_for_mem_leak man ~assert_exp_imprecise:true ~exp:(Some exp)
	end
	end;
	state

In particular, it should probably only be handled when Assert has refine = true or something.

[michael-schwarz]

Yeah, this is to handle the case of program execution ending at an assert (because then the memory is usually not cleaned up). Only invoking this in case refine = true sounds reasonable.