Put `retrieveGaData test1 = new retrieveGAdata();` *after* `Test.setMock`. That's the only line of code that could execute a callout as far as I can see.

    public static testmethod  void testsaveDataToSF()
    {
        // other setup
        Test.setMock(HttpCalloutMock.class, multiCalloutMock);
        retrieveGaData test1 = new retrieveGAdata();
    }