Do not touch cache on ZoneInfoDb::hasTimeZone.

Replaced possible cache update with existence check in
ids array.

Bug: 173787057
Test: Presubmit only.
Change-Id: Iaf14310481fa8173239d9944489dd806e400b867
diff --git a/android_icu4j/libcore_bridge/src/java/com/android/i18n/timezone/ZoneInfoDb.java b/android_icu4j/libcore_bridge/src/java/com/android/i18n/timezone/ZoneInfoDb.java
index afa10ac..2782efa 100644
--- a/android_icu4j/libcore_bridge/src/java/com/android/i18n/timezone/ZoneInfoDb.java
+++ b/android_icu4j/libcore_bridge/src/java/com/android/i18n/timezone/ZoneInfoDb.java
@@ -390,7 +390,7 @@
   @libcore.api.CorePlatformApi
   public boolean hasTimeZone(String id) {
     checkNotClosed();
-    return cache.get(id) != null;
+    return Arrays.binarySearch(ids, id) >= 0;
   }
 
   // VisibleForTesting