server-del: update defaultServerList in cn=default,ou=profile,$BASE
    
    ipa server-del should remove the server from the entry
    cn=default,ou=profile,$BASE
    The entry contains an attribute
    defaultServerList: srv1.domain.com srv2.domain.com srv3.domain.com
    
    The code calls srvlist = ret.single_value.get('defaultServerList') which means
    that srvlist contains a single value (string) containing all the servers
    separated by a space, and not a list of attribute values. Because of that,
    srvlist[0] corresponds to the first character of the value.
    The fix splits srvlist and not srvlist[0].
    
    https://pagure.io/freeipa/issue/6943
    
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>