Fix For Wildcard-containing only_db failure in sidebar

This commit fixes the Bug #4242. The only_db now accepts mySQL
LIKE wildcards without errors.Changes have been made to the function
getData() in phpmyadmin/libraries/navigation/Nodes/Node.class.php .
The if-else clause has been removed. The checking of the "only_db"
directive is now performed solely by the function
getWhereClause()in the same class.