Fix scrape service test

[penmanglewood]

#43 changed the function signature for newPagespeedScrapeService, but the test file was not updated.

This PR fixes that syntax error and additionally it allows the non-short version of the test to authenticate against the Pagespeed API to run the full test.

The tests can be run as follows:

# run all tests, skipping the scrape service test
go test -short ./... 

# runs all tests, but skips the scrape service test because the api key
# and credentials file envvars are not set
go test ./...

# runs all tests, including the scrape service integration test, calling the real Pagespeed API
export PAGESPEED_API_KEY=yourapikey
go test ./...

# same as above
export PAGESPEED_CREDENTIALS_FILE=/path/to/credentials.json
go test ./...

[penmanglewood]

Thank you @smartinov and sorry for the trouble 🙏

[smartinov]

@penmanglewood no trouble at all! Thank you for the contribution!