pgsql: Trivial dead code removal: in CreateSchemaCommand(), 'owner_name'

Log Message:
-----------
Trivial dead code removal: in CreateSchemaCommand(), 'owner_name' is
only used in one branch of an if statement, so we can move its
declaration to that block. This also avoids an unnecessary syscache
lookup.

Per Coverity static analysis performed by EnterpriseDB.

Modified Files:
--------------
pgsql/src/backend/commands:
schemacmds.c (r1.29 -> r1.30)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/schemacmds.c.diff?r1=1.29&r2=1.30)