ipatests: add a test for stageuser-find with non-posix account
Add a new XMLRPC test with the following scenario:
- ldapadd a user without the posixaccount objectclass
- call ipa stageuser-find <user>
- check that 1 entry is returned
Related: https://pagure.io/freeipa/issue/7983
Reviewed-By: Rob Crittenden <rcritten@redhat.com>