Renaming recenly added test case, because of name conflict

when merging into 5.1.


mysql-test/t/rpl_loaddata_charset.test:
  Rename: mysql-test/t/rpl_loaddata2.test -> mysql-test/t/rpl_loaddata_charset.test
mysql-test/r/rpl_loaddata_charset.result:
  Rename: mysql-test/r/rpl_loaddata2.result -> mysql-test/r/rpl_loaddata_charset.result