Don't cause exception checking for retry
Expand test to general cover all DML
Save Schema used in all Statements and require set before use on context
Be consistent in OnlineHelper
merge nathanlws: Use proper qp.Schema from Statements with cached plans

Merge pull request #1299 from nathanlws/sql-layer/fix-cached-plan-changing-schema
https://github.com/FoundationDB/sql-layer/pull/1299