[FixRM #8319] - Properly disable BLANK_PASSWORDS for ektron_cms400net

In module ektron_cms400net.rb, datastore option "BLANK_PASSWORDS" is set to false by default, because according to the original author, a blank password will result in account lockouts. Since the user should never set "BLANK_PASSWORDS" to true, this option should never be presented as an option (when issuing the "show options").

See:
http://dev.metasploit.com/redmine/issues/8319

While fixing #8319, I also noticed another bug at line 108, where res.code is used when res could be nil due to a timeout, so I ended up fixing it, too.