On-device signing: switch to using Keystore2.

Now that Keystore2 has landed, switch to using that, instead of talking
to Keymaster directly.

Bug: 165630556
Test: inspect logs
Change-Id: I8a5b3cafd96a5b2782901165030bd60e06c0b944
diff --git a/ondevice-signing/odsign_main.cpp b/ondevice-signing/odsign_main.cpp
index 58e49ec..33d04ca 100644
--- a/ondevice-signing/odsign_main.cpp
+++ b/ondevice-signing/odsign_main.cpp
@@ -56,7 +56,7 @@
 static const char* kFsVerityProcPath = "/proc/sys/fs/verity";
 
 static const bool kForceCompilation = false;
-static const bool kUseKeystore = false;
+static const bool kUseKeystore = true;
 
 static const char* kOdsignVerificationDoneProp = "odsign.verification.done";
 static const char* kOdsignKeyDoneProp = "odsign.key.done";