TDI-30681 fix bug: TUJ regression on 5.6 on Bug_TDI_24212_tELTJDBCXXX
https://jira.talendforge.org/browse/TDI-30681

Alias name _String is not allowed in the Oracle database select query;
before the ELT feature(TDI-29674), there is no alias name for the select
query, and no deliver table too.
So I change the logic, only add the alias name for the deliver table,
means the alias name will not effect the older jobs(because no deliver
table) before this feature any more.