ipaidview: Fail to apply unknown (invalid) hosts

The task to apply an unknown (invalid) host to an idview was not failing
as expected and only reported no change.

A new host verification step has been added to fail before trying to
apply invalid hosts. unapplying an invalid host is not failing as the
invalid host is indeed not applied.

plugins/modules/ipaidview.py

@@ -127,7 +127,7 @@ RETURN = """
 
 from ansible.module_utils.ansible_freeipa_module import \
     IPAAnsibleModule, compare_args_ipa, gen_add_del_lists, gen_add_list, \
-    gen_intersection_list
+    gen_intersection_list, ipalib_errors
 from ansible.module_utils import six
 
 if six.PY3:
@@ -144,6 +144,14 @@ def find_idview(module, name):
     return _result["result"]
 
 
+def valid_host(module, name):
+    try:
+        module.ipa_command("host_show", name, {})
+    except ipalib_errors.NotFound:
+        return False
+    return True
+
+
 def gen_args(description, domain_resolution_order):
     _args = {}
     if description is not None:
@@ -327,6 +335,9 @@ def main():
 
             # Add members
             if host_add:
+                for host in host_add:
+                    if not valid_host(ansible_module, host):
+                        ansible_module.fail_json("Invalid host '%s'" % host)
                 commands.append([name, "idview_apply", {"host": host_add}])
 
             # Remove members