Make states atomic and update comments

Bug: 166800618
Test: atest VtsHalBiometricsFingerprintTargetTest
Change-Id: I52ee6e8b6ddefdc972e803bcd81819f04061a570
diff --git a/biometrics/fingerprint/aidl/default/Session.cpp b/biometrics/fingerprint/aidl/default/Session.cpp
index f6a0314..8db3205 100644
--- a/biometrics/fingerprint/aidl/default/Session.cpp
+++ b/biometrics/fingerprint/aidl/default/Session.cpp
@@ -46,7 +46,7 @@
 
 void Session::enterStateOrCrash(int cookie, SessionState state) {
     CHECK(mScheduledState == state);
-    mCurrentState = mScheduledState;
+    mCurrentState = state;
     mScheduledState = SessionState::IDLING;
     mCb->onStateChanged(cookie, mCurrentState);
 }