ipa-adtrust-install: remove wrong check for dm_password

Additionally this patch removes a comment which makes no sense at this
place anymore.

Fixes https://fedorahosted.org/freeipa/ticket/3023

install/tools/ipa-adtrust-install

@@ -194,10 +194,6 @@ def main():
         print "Please wait until the prompt is returned."
         print ""
 
-    # Create a Adtrust instance
-    if options.unattended and not options.dm_password:
-        sys.exit("\nIn unattended mode you need to provide at least the -p option")
-
     netbios_name = options.netbios_name
     if not netbios_name:
         netbios_name = adtrustinstance.make_netbios_name(api.env.domain)