make setSnapshot synchronized

Signed-off-by: Sebastian Schepens <[email protected]>

Author: sschepens

cache/src/main/java/io/envoyproxy/controlplane/cache/SimpleCache.java

@@ -196,7 +196,7 @@ public Collection<T> groups() {
    * {@inheritDoc}
    */
   @Override
-  public void setSnapshot(T group, Snapshot snapshot) {
+  public synchronized void setSnapshot(T group, Snapshot snapshot) {
     // we take a writeLock to prevent watches from being created while we update the snapshot
     CacheStatusInfo<T> status;
     writeLock.lock();