tools: update the leader transfer example (#553)

lilin90 · CaitinChen · commit 3f18e59bdcb8 · 2018-07-30T13:10:59.000+08:00
Via: pingcap/docs-cn#819
diff --git a/tools/pd-control.md b/tools/pd-control.md
@@ -340,7 +340,7 @@ Success!
 }
 >> member leader resign // Move leader away from the current member
 ......
->> member leader transfer 9724873857558226554 // Migrate leader to a specified ID member
+>> member leader transfer pd3 // Migrate leader to a specified member
 ......
 ```
 

Original file line number	Diff line number	Diff line change
`@@ -340,7 +340,7 @@ Success!`
`340`	`340`	`}`
`341`	`341`	`>> member leader resign // Move leader away from the current member`
`342`	`342`	`......`
`343`		`->> member leader transfer 9724873857558226554 // Migrate leader to a specified ID member`
	`343`	`+>> member leader transfer pd3 // Migrate leader to a specified member`
`344`	`344`	`......`
`345`	`345`	```
`346`	`346`