[INTERNAL] [FIX] grunt: fix usage of port parameter
[INTERNAL] [FIX] grunt: fix usage of port parameter

When using `npm start -- --port=9090`, port parameter is always string.

Change-Id: I2a236fd68f560de84cb99e660c48c3ca15815fb7

nzamani/openui5,SQCLabs/openui5,nzamani/openui5,SAP/openui5,olirogers/openui5,olirogers/openui5,SAP/openui5,SAP/openui5,cschuff/openui5,cschuff/openui5,SAP/openui5,nzamani/openui5,SQCLabs/openui5,cschuff/openui5,olirogers/openui5,SQCLabs/openui5