homectl,TEST-46: fix test and fix homectl return value, update docs

The usual: the test wasn't testing, so we didn't notice that the
command wasn't returning as expected.

src/home/homectl.c

@@ -3362,4 +3362,4 @@ static int run(int argc, char *argv[]) {
         return dispatch_verb(argc, argv, verbs, NULL);
 }
 
-DEFINE_MAIN_FUNCTION(run);
+DEFINE_MAIN_FUNCTION_WITH_POSITIVE_FAILURE(run);