test: make hive.store.TestHiveStore.testAutoCreateSchema deterministic

[Jack-LuoHongyi]

Title: test: make org.apache.gora.hive.store.TestHiveStore deterministic

Summary

• Type: timing-safe assertion (metastore visibility)
• Scope: test-only; no production changes
• Module: gora-hive
• Test: org.apache.gora.hive.store.TestHiveStore#testAutoCreateSchema

Root Cause
After auto-creating the table, Hive metastore visibility may lag briefly. A direct schemaExists() check immediately after the first write can observe stale metadata.

Fix

• Move the wait-for-visibility logic into assertAutoCreateSchema only. Poll up to 5 seconds (100 ms interval) with flush() between attempts until schemaExists() is observed, then assert. The timeout balances reliability and runtime overhead.
• Keep assertSchemaExists as a direct existence check and handle both Employee and WebPage schema names (base tests call assertSchemaExists("WebPage") in DataStoreTestBase#testTruncateSchema).
• Resolve the schema name via employeeStore.getSchemaName() to remain robust to mapping changes.

Validation

• Local: executed mvn -pl gora-hive -Dtest=org.apache.gora.hive.store.TestHiveStore#testAutoCreateSchema test
• Scope: test-only changes; no production impact

Risk
Low. Adds a bounded wait in a single test path; preserves validation semantics.