fix: winrt: Return error when discovering services fails

Prior to this commit, the `discover_services` method would return
`Ok(())` even if the underlying calls had failed.

src/winrtble/peripheral.rs

@@ -454,6 +454,7 @@ impl ApiPeripheral for Peripheral {
                         }
                         Err(e) => {
                             error!("get_characteristics_async {:?}", e);
+                            return Err(e);
                         }
                     }
                 }