allow host name as remote ip (#2550)

Co-authored-by: liuzhe <zhe.liu@microsoft.com>

docs/en_US/Tutorial/ExperimentConfig.md

@@ -528,9 +528,9 @@ Required in remote mode. A list of key-value pairs with the following keys.
 
 #### ip
 
-Required. IP address that is accessible from the current machine.
+Required. IP address or host name that is accessible from the current machine.
 
-The IP address of remote machine.
+The IP address or host name of remote machine.
 
 #### port
 

src/nni_manager/rest_server/restValidationSchemas.ts

@@ -10,7 +10,7 @@ export namespace ValidationSchemas {
         body: {
             machine_list: joi.array().items(joi.object({ // eslint-disable-line @typescript-eslint/camelcase
                 username: joi.string().required(),
-                ip: joi.string().ip().required(),
+                ip: joi.string().hostname().required(),
                 port: joi.number().min(1).max(65535).required(),
                 passwd: joi.string(),
                 sshKeyPath: joi.string(),