Stop using a magic wait time and clean-up the code

cmd/soroban-rpc/internal/test/cli_test.go

@@ -7,7 +7,6 @@ import (
 	"os"
 	"strings"
 	"testing"
-	"time"
 
 	"github.com/creachadair/jrpc2"
 	"github.com/creachadair/jrpc2/jhttp"
@@ -197,7 +196,7 @@ func runSuccessfulCLICmd(t *testing.T, cmd string) string {
 	return strings.TrimSpace(stdout)
 }
 
-func cliCmd(t *testing.T, cmd string) icmd.Cmd {
+func runCLICommand(t *testing.T, cmd string) *icmd.Result {
 	args := []string{"run", "-q", "--", "--vv"}
 	parsedArgs, err := shlex.Split(cmd)
 	require.NoError(t, err, cmd)
@@ -207,7 +206,7 @@ func cliCmd(t *testing.T, cmd string) icmd.Cmd {
 		fmt.Sprintf("SOROBAN_RPC_URL=http://localhost:%d/", sorobanRPCPort),
 		fmt.Sprintf("SOROBAN_NETWORK_PASSPHRASE=%s", StandaloneNetworkPassphrase),
 	)
-	return c
+	return icmd.RunCmd(c)
 }
 
 func getCLIDefaultAccount(t *testing.T) string {