Description of problem:
[WebUI] Error message could be better while adding idrange with untrusted
domain name.

Version-Release number of selected component (if applicable):
ipa-server-4.1.0-18.el7_1.3.x86_64

How reproducible:
100%

Steps to Reproduce:
1.Navigate to "ID Range" page
2. Select Add >> Enter "Range name" >>
   Select "Range type" -> Active Directory domain with POSIX attributes>
   Add "Base ID", "Range size" and
   Enter untrusted domain name in "Name of the trusted domain" field
3.Hit Add

Actual results:
"invalid 'ID Range setup': SID for the specified trusted domain name could not
be found. Please specify the SID directly using dom-sid option."

Expected results:
Specified trusted domain name could not be found.

Additional info:
Actually SID option is now replaced by domain in IPA 4.1 and SID will be
automatically resolved from the domain name. so the above error message does
not seem appropriate.