fuzz: cover BanMan::IsDiscouraged

Author: brunoerg

src/test/fuzz/banman.cpp

@@ -117,6 +117,9 @@ FUZZ_TARGET(banman, .init = initialize_banman)
                 },
                 [&] {
                     ban_man.Discourage(ConsumeNetAddr(fuzzed_data_provider));
+                },
+                [&] {
+                    ban_man.IsDiscouraged(ConsumeNetAddr(fuzzed_data_provider));
                 });
         }
         if (!force_read_and_write_to_err) {