[system-tests] Reconnect sl4f client when retrying OTA

Bug: 109811
Change-Id: I18bfefba38358c06578a0cf0aaa0bc5c8e463eff
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/742542
Reviewed-by: Erick Tryzelaar <[email protected]>
Commit-Queue: Erick Tryzelaar <[email protected]>

Author: kellerb

src/sys/pkg/tests/system-tests/upgrade_test/upgrade_test.go

@@ -239,6 +239,16 @@ func doTestOTAs(
 				return fmt.Errorf("failed to create ota test client: %w", err)
 			}
 			*device = *newClient
+
+			if rpcClient != nil && *rpcClient != nil {
+				(*rpcClient).Close()
+				*rpcClient = nil
+			}
+
+			*rpcClient, err = device.StartRpcSession(ctx, repo)
+			if err != nil {
+				return fmt.Errorf("unable to connect to sl4f while retrying OTA: %w", err)
+			}
 		}
 
 		if !successfulNMinusOneToN {