Restore USERNAME and PASSWORD options for owa_login

Requested by our own pentesters, the username & password options
should be restored so users can more easily try one password but
multiple users.

Author: wchen-r7

modules/auxiliary/scanner/http/owa_login.rb

@@ -92,7 +92,7 @@ def initialize
         OptString.new('AD_DOMAIN', [ false, "Optional AD domain to prepend to usernames", ''])
       ], self.class)
 
-    deregister_options('BLANK_PASSWORDS', 'RHOSTS','PASSWORD','USERNAME')
+    deregister_options('BLANK_PASSWORDS', 'RHOSTS')
   end
 
   def setup