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
Merged-In: If5a90d62f77489aa58f96e908553a052cf6d1e18
(cherry picked from commit 43dd6e34)