fastboot: Print OemCmdHandler return message on success

This allows OEM commands to print messages in fastboot output.

Test: run fastboot oem getprop ro.boot.rf_version
      and observe property value being printed in console

Change-Id: Id9bd5a107861a790cd02dc87057600de5bb94d42
diff --git a/fastboot/device/commands.cpp b/fastboot/device/commands.cpp
index b9f6c97..0f3a208 100644
--- a/fastboot/device/commands.cpp
+++ b/fastboot/device/commands.cpp
@@ -254,6 +254,7 @@
         return device->WriteStatus(FastbootResult::FAIL, ret.message);
     }
 
+    device->WriteInfo(ret.message);
     return device->WriteStatus(FastbootResult::OKAY, ret.message);
 }