Allow unlocked in VTS

VTS was running on a userdebug build GSI before Android 10.
Starting from Android 10, VTS is switched to running on top of a
user build GSI image, plus the device-specific boot-debug.img to
allow adb root.

   https://source.android.com/compatibility/vts/vts-on-gsi

So 'ro.build.type' will be 'user' because the value comes from
/system/build.prop. Switching to using 'ro.debuggable' to decide
whether we should check the device is locked or not. Note that
'ro.debuggable' will be '1' for userdebug/eng images or when a
boot-debug.img is used.

Bug: 154449286
Test: atest VtsHalKeymasterV4_0TargetTest
Change-Id: If5a90d62f77489aa58f96e908553a052cf6d1e18

keymaster/4.0/vts/functional/keymaster_hidl_hal_test.cpp

@@ -438,10 +438,10 @@ bool verify_attestation_record(const string& challenge, const string& app_id,
             EXPECT_TRUE(device_locked);
         }
 
-        // Check that the expected result from VBMeta matches the build type. Only a user build
-        // should have AVB reporting the device is locked.
-        EXPECT_NE(property_get("ro.build.type", property_value, ""), 0);
-        if (!strcmp(property_value, "user")) {
+        // Check that the device is locked if not debuggable, e.g., user build
+        // images in CTS. For VTS, debuggable images are used to allow adb root
+        // and the device is unlocked.
+        if (!property_get_bool("ro.debuggable", false)) {
             EXPECT_TRUE(device_locked);
         } else {
             EXPECT_FALSE(device_locked);