crash_test to enable block-based table hash index (#6310)

Summary:
Block-based table has index has been disabled in crash test due to bugs. We fixed a bug and re-enable it.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6310

Test Plan: Finish one round of "crash_test_with_atomic_flush" test successfully while exclusively running has index. Another run also ran for several hours without failure.

Differential Revision: D19455856

fbshipit-source-id: 1192752d2c1e81ed7e5c5c7a9481c841582d5274

tools/db_crashtest.py

@@ -52,8 +52,7 @@ default_params = {
     "expected_values_path": expected_values_file.name,
     "flush_one_in": 1000000,
     "get_live_files_and_wal_files_one_in": 1000000,
-    # Temporarily disable hash index
-    "index_type": lambda: random.choice([0,2]),
+    "index_type": lambda: random.choice([0, 0, 1, 2, 2]),
     "max_background_compactions": 20,
     "max_bytes_for_level_base": 10485760,
     "max_key": 100000000,
@@ -236,6 +235,9 @@ def finalize_and_sanitize(src_params):
             dest_params["partition_filters"] = 0
         else:
             dest_params["use_block_based_filter"] = 0
+    if dest_params["index_type"] == 1 and \
+        dest_params.get("prefix_size", 7) == -1:
+        dest_params["index_type"] = 0       
     if dest_params.get("atomic_flush", 0) == 1:
         # disable pipelined write when atomic flush is used.
         dest_params["enable_pipelined_write"] = 0