fix: Don't check if the service is running to stop Percy (#581)

This approach assumes running `percy stop` will happen in the same session. The
better approach is to send the POST request anyways & catch if it fails. That
way if the server is running (on that path/port) it will get stopped.

src/commands/stop.ts

@@ -34,18 +34,16 @@ export default class Stop extends PercyCommand {
     const { flags } = this.parse(Stop)
     const configuration = config(flags)
 
-    if (this.processService.isRunning()) {
-      await this.postToRunningAgent(STOP_PATH, configuration.agent.port)
-    } else {
-      this.logger.warn('percy is already stopped.')
-    }
+    await this.postToRunningAgent(STOP_PATH, configuration.agent.port)
   }
 
   private async postToRunningAgent(path: string, port: number) {
     await Axios(`http://localhost:${port}${path}`, { method: 'POST' })
       .catch((error: any) => {
         if (error.message === 'socket hang up') { // We expect a hangup
           this.logger.info('percy stopped.')
+        } else if (error.code === 'ECONNREFUSED') {
+          this.logger.info('percy is already stopped.')
         } else {
           logError(error)
         }