[CBRD-24909] dblink related synonym processing

[beyondykk9]

http://jira.cubrid.org/browse/CBRD-24909

The current system checks the user set in the synonym target when creating or altering a synonym. However, if the target is the dblink table of a remote server, user check cannot be performed. In this case, the user check must be replaced with the current user, and the target Also, the text entered by the user who created it must be reflected as it is.

CREATE SYNONYM rms1 for user_a.tbl1@srv1;
CREATE SYNONYM rms2 for tbl2@srv1;
ALTER SYNONYM rms1 for user_b.tbl1@srv1;
ALTER SYNONYM rms2 for tbl2@srv2;

The above DDL should be executed successfully.