Support 'fastboot getvar unlocked' command.

Test: fastboot getvar unlocked.
Bug: 78793464

Change-Id: Ie59c6db90a503e9a6e9ac1c416e4ee5deac60479
diff --git a/fastboot/device/variables.cpp b/fastboot/device/variables.cpp
index 7535248..002e043 100644
--- a/fastboot/device/variables.cpp
+++ b/fastboot/device/variables.cpp
@@ -148,7 +148,7 @@
 
 bool GetUnlocked(FastbootDevice* /* device */, const std::vector<std::string>& /* args */,
                  std::string* message) {
-    *message = "yes";
+    *message = GetDeviceLockStatus() ? "no" : "yes";
     return true;
 }