wu-ftpd ftpaccess `restricted-uid'/`restricted-gid' directive may be bypassed

Glenn Stewart reports a bug in wu-ftpd's ftpaccess `restricted-uid'/`restricted-gid' directives:

Users can get around the restriction to their home directory by issuing a simple chmod command on their home directory. On the next ftp log in, the user will have '/' as their root directory.

Matt Zimmerman discovered that the cause of the bug was a missing check for a restricted user within a code path that is executed only when a certain error is encountered.