Fix crypt() return value check to match PHP documentation

PHP documentation states:

"Returns the hashed string or a string that is shorter than 13 characters and is
guaranteed to differ from the salt on failure." [1]

Therefore, the check should be looking for a string length "less than 13"
characters rather than "less than or equal to 13" characters.

[1] http://php.net/function.crypt.php
Merge branch 'gwis-fix-crypt-retval-check'