Revert "ext/pdo_mysql/tests/pdo_mysql_attr_oracle_nulls.phpt fails in trunk as well while building with libmysql"

This reverts commit 29b35292923596413a0fbf49890a2cbb16cbf8b4.
ext/pdo_mysql/tests/pdo_mysql_attr_oracle_nulls.phpt fails in trunk as well while building with libmysql