Investigate undeleteTable IT flakiness

[stephaniewang526]

A discrepancy between backend snapTime and our sample's System.currentTimeMillis() (

java-bigquery/samples/snippets/src/main/java/com/example/bigquery/UndeleteTable.java

Line 50 in 38c8716

long snapTime = System.currentTimeMillis();

) when running the IT in Java 11 on Kokoro is causing persistent failures.

Error details:

 BigQuery was unable to copy the table due to an error:
    BigQueryError{reason=invalid, location=null, message=Invalid snapshot time 1600273978360 for table java-docs-samples-testing:bigquery_test_dataset.UNDELETE_TABLE_TEST_789cbad2@1600273978360. Cannot read before 1600273978399}

full sponge log

Note that this is not happening when running the IT locally and it consistently fails for Java 11 test on Kokoro. We may need to change local test env to Java 11 and see if we can repro this.

TODO: We need to revert this PR when this issues is fixed: #735