Addded new env for force download binary LT_FORCE_DOWNLOAD

Author: kanhaiya

lib/tunnel_binary.js

@@ -205,7 +205,7 @@ function TunnelBinary(httpTunnelConfig) {
       }
       var binaryPath = path.join(destParentDir, destBinaryName);
       // Check whether executable binary File is exist or need to Downlaod.
-      if (this.checkPath_(binaryPath, fs.X_OK)) {
+      if (this.checkPath_(binaryPath, fs.X_OK) && !process.env.LT_FORCE_DOWNLOAD) {
         var that = this;
         console.log(`Checking for updates`);
         // Comparing with local hash to find out binary changes.
@@ -222,6 +222,7 @@ function TunnelBinary(httpTunnelConfig) {
           that.download_(conf, destParentDir, 5, fnCallback);
         }
       } else {
+        delete process.env.LT_FORCE_DOWNLOAD;
         this.download_(conf, destParentDir, 5, fnCallback);
       }
     } catch (e) {