KeyMint VTS: extract full vendor patchlevel

The vendor patchlevel is YYYYMMDD not YYYYMM

Bug: 188672564
Bug: 186735514
Test: VtsAidlKeyMintTargetTest
Merged-In: Ia641f8eef84a85aec8f2a0551c192b6874301126
Change-Id: Ia641f8eef84a85aec8f2a0551c192b6874301126
Ignore-AOSP-First: already present in aosp/master
1 file changed