sdk: call /hello with ledger name

`/hello` defaults to returning information about `ordev` when
`ledger_name` is not specified. `ledger_name` will be used to
determine a ledger's region from the central stack.

Closes #4573

Author: Dominic Dagradi <ddagradi@gmail.com>
Date: Tue Aug 7 16:25:56 2018 -0700
upstream:2a2a6be96eb605becc9e8332ddc9470be01e6f9e

Author: dominic

src/connection.ts

@@ -286,7 +286,9 @@ export class Connection {
   public async getLedgerUrl() {
     const body = (await this.requestRaw(
       'https://' + (process.env.SEQADDR || 'api.seq.com') + '/hello',
-      {},
+      {
+        ledger_name: this.ledgerName,
+      },
       { Credential: this.credential }
     )) as any