function makeGcpRequest(params, callback) {
    const { method, queryObj, headers, bucket, objectKey, authCredentials,
        requestBody } = params;
    const options = {
        authCredentials,
        requestBody,
        hostname: 'storage.googleapis.com',
        port: 80,
        method,
        queryObj,
        headers: headers || {},
        path: bucket ? `/${bucket}/` : '/',
        GCP: true,
    };
    if (objectKey) {
        options.path = `${options.path}${objectKey}`;
    }
    makeRequest(options, callback);
}
makeGcpRequest - utility function to generate a request against GCP
@param {object} params - params for making request
@param {string} params.method - request method
@param {object} [params.queryObj] - query fields and their string values
@param {object} [params.headers] - headers and their string values
@param {string} [params.bucket] - bucket name
@param {string} [params.objectKey] - object key name
@param {object} [params.authCredentials] - authentication credentials
@param {object} params.authCredentials.accessKey - access key
@param {object} params.authCredentials.secretKey - secret key
@param {function} callback - with error and response parameters
@return {undefined} - and call callback