Don't clean the destination app folder when webpack process is already running. (#535)

Fixes the case when the user executes the following commands:
tns run android --bundle --release --env.snapshot
tns run android --bundle

Author: Fatme

lib/before-cleanApp.js

@@ -1,8 +1,15 @@
 const { cleanSnapshotArtefacts } = require("../snapshot/android/project-snapshot-generator");
 const { isAndroid } = require("../projectHelpers");
+const { getWebpackProcess } = require("./compiler");
 
 module.exports = function (hookArgs) {
-    if (isAndroid(hookArgs.platformInfo.platform)) {
-        cleanSnapshotArtefacts(hookArgs.platformInfo.projectData.projectDir);
+    return (args, originalMethod) => {
+        const webpackProcess = getWebpackProcess();
+        const promise = webpackProcess ? Promise.resolve() : originalMethod(...args);
+        return promise.then(() => {
+            if (isAndroid(hookArgs.platformInfo.platform)) {
+                cleanSnapshotArtefacts(hookArgs.platformInfo.projectData.projectDir);
+             }
+        });
     }
 }