java-datastore: LocalDatastoreHelper is downloading datastore emulator zip every time even when file exists

[ekuleshov]

When the LocalDatastoreHelper is started with .start() API it is downloading a 36mb zip file from http://storage.googleapis.com/gcd/tools/cloud-datastore-emulator-2.3.1.zip every time even if file already exist locally.

This is due to checksum mismatch at:

https://github.com/googleapis/sdk-platform-java/blob/56aa3438393e1992bb8f688291fb12030ec9bc0e/java-core/google-cloud-core/src/main/java/com/google/cloud/testing/BaseEmulatorHelper.java#L465-L479

The checksum value that LocalDatastoreHelper is passing down is not correct:

google-cloud-java/java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/testing/LocalDatastoreHelper.java

Line 68 in aa2c249

private static final String MD5_CHECKSUM = "e0d1170519cf52e2e5f9f93892cdf70c";

The actual file checksum is 7c1f5a3276241a8f78cb1a837daaaa47:

> curl http://storage.googleapis.com/gcd/tools/cloud-datastore-emulator-2.3.1.
zip | md5sum
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 36.1M  100 36.1M    0     0  8831k      0  0:00:04  0:00:04 --:--:-- 8833k
7c1f5a3276241a8f78cb1a837daaaa47  -