Check return status of ReadFileToString() in GetDeviceLockStatus()

Return lock status of true if unable to read kernel command line.

Test: fastboot getvar unlocked
Bug: 117275849
Change-Id: Id6c00c769bcdcdf87fcc9e88902713a8eff3e320
diff --git a/fastboot/device/utility.cpp b/fastboot/device/utility.cpp
index 30c5960..b844b9f 100644
--- a/fastboot/device/utility.cpp
+++ b/fastboot/device/utility.cpp
@@ -169,6 +169,9 @@
 
 bool GetDeviceLockStatus() {
     std::string cmdline;
-    android::base::ReadFileToString("/proc/cmdline", &cmdline);
+    // Return lock status true if unable to read kernel command line.
+    if (!android::base::ReadFileToString("/proc/cmdline", &cmdline)) {
+        return true;
+    }
     return cmdline.find("androidboot.verifiedbootstate=orange") == std::string::npos;
 }