Prevent afl-fuzz from modifying stage_max during fuzzing

src/afl-fuzz-one.c

@@ -1767,6 +1767,8 @@ custom_mutator_stage:
 
             }
 
+            if (!el->afl_custom_fuzz_count) {
+
               /* If we're finding new stuff, let's run for a bit longer, limits
                 permitting. */
 
@@ -1785,6 +1787,8 @@ custom_mutator_stage:
 
             }
 
+          }
+
           /* `(afl->)out_buf` may have been changed by the call to custom_fuzz
            */
           /* TODO: Only do this when `mutated_buf` == `out_buf`? Branch vs