Reduce end session delay for default IVibratorManager

Reduce fake delay for default implementation of HAL service
IVibratorManager to avoid flakiness in VTS tests.

The tests allow for a timeout of 100ms for ending a vibration session,
and the fake delay was too high at 50ms.

Change-Id: I519f73a477494cc0823249ca16c0925f22134dfb
Fix: 379204591
Flag: EXEMPT update default HAL implementation
Test: VtsHalVibratorManagerTargetTest
diff --git a/vibrator/aidl/default/VibrationSession.cpp b/vibrator/aidl/default/VibrationSession.cpp
index cfb6608..4eac831 100644
--- a/vibrator/aidl/default/VibrationSession.cpp
+++ b/vibrator/aidl/default/VibrationSession.cpp
@@ -24,7 +24,7 @@
 namespace hardware {
 namespace vibrator {
 
-static constexpr int32_t SESSION_END_DELAY_MS = 50;
+static constexpr int32_t SESSION_END_DELAY_MS = 20;
 
 ndk::ScopedAStatus VibrationSession::close() {
     LOG(VERBOSE) << "Vibration Session close";