Suppress 404 Not Found error in xxxTableIfExists methods

[xerial]

If we know 404 can be returned, we should be able to configure expected error types in TDHttpClient to suppress error messages like this:

2017-11-01 08:44:52.462 DEBUG [main] TDHttpClient [404:Not Found] API request to /v3/table/delete/_tdclient_test/sample2_20171101084452261 has failed: Resource not found 
2017-11-01 08:44:52.463 WARN  [main] TDHttpClient API request failed 
com.treasuredata.client.TDClientHttpNotFoundException: [TARGET_NOT_FOUND] [404:Not Found] API request to /v3/table/delete/_tdclient_test/sample2_20171101084452261 has failed: Resource not found
	at com.treasuredata.client.TDHttpClient.handleHttpResponseError(TDHttpClient.java:510) [classes/:na]
	at com.treasuredata.client.TDHttpClient.submitRequest(TDHttpClient.java:399) [classes/:na]
	at com.treasuredata.client.TDHttpClient.submitRequest(TDHttpClient.java:465) [classes/:na]
	at com.treasuredata.client.TDHttpClient.call(TDHttpClient.java:575) [classes/:na]
	at com.treasuredata.client.TDClient.doPost(TDClient.java:251) [classes/:na]
	at com.treasuredata.client.TDClient.deleteTable(TDClient.java:458) [classes/:na]
	at com.treasuredata.client.TDClient.deleteTableIfExists(TDClient.java:466) [classes/:na]