Call plugin teardown method when plugin is destroyed

Summary: `teardown()` was not called for device plugins. This diff fixes the issue.

Reviewed By: jknoxville

Differential Revision: D16416440

fbshipit-source-id: 5c9ffa211bfbe4e322504c37b95ff87afab8d061

src/plugin.js

@@ -164,6 +164,10 @@ export class FlipperDevicePlugin<S = *, A = *, P = *> extends FlipperBasePlugin<
     this.init();
   }
 
+  _teardown() {
+    this.teardown();
+  }
+
   static supportsDevice(device: BaseDevice) {
     throw new Error(
       'supportsDevice is unimplemented in FlipperDevicePlugin class',