Use built-in cmp python function in comparing Datastore paths

[vikkyrk]

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[vikkyrk]

R: @aaltay

[aaltay]

LGTM, I can merge after tests.

Is there a unit test for compare_path ?

[vikkyrk]

Yes they are here, https://github.com/apache/beam/blob/master/sdks/python/apache_beam/io/gcp/datastore/v1/helper_test.py. The problem is that query_splitter isn't being tested for both name and id. Fixed that.

[coveralls]

Changes Unknown when pulling b3124b1 on vikkyrk:ds_py into ** on apache:master**.

[aaltay]

Thank you, LGTM. (I can merge after new tests.)

[coveralls]

Coverage remained the same at 70.222% when pulling b3124b1 on vikkyrk:ds_py into 69522fe on apache:master.