Fix reactive streams MongoClient.getTimeout always returning null

driver-reactive-streams/src/main/com/mongodb/reactivestreams/client/internal/MongoClientImpl.java

@@ -291,8 +291,9 @@ public ReadConcern getReadConcern() {
     }
 
     @Override
+    @Nullable
     public Long getTimeout(final TimeUnit timeUnit) {
-        return null;
+        return delegate.getTimeout(timeUnit);
     }
 
     @Override

driver-reactive-streams/src/main/com/mongodb/reactivestreams/client/internal/MongoClusterImpl.java

@@ -91,9 +91,11 @@ public ReadConcern getReadConcern() {
     }
 
     @Override
+    @Nullable
     public Long getTimeout(final TimeUnit timeUnit) {
+        notNull("timeUnit", timeUnit);
         Long timeoutMS = mongoOperationPublisher.getTimeoutMS();
-        return timeoutMS != null ? MILLISECONDS.convert(timeoutMS, timeUnit) : null;
+        return timeoutMS == null ? null : timeUnit.convert(timeoutMS, MILLISECONDS);
     }
 
     @Override

driver-sync/src/main/com/mongodb/client/internal/MongoClientImpl.java

@@ -167,6 +167,7 @@ public ReadConcern getReadConcern() {
     }
 
     @Override
+    @Nullable
     public Long getTimeout(final TimeUnit timeUnit) {
         return delegate.getTimeout(timeUnit);
     }

driver-sync/src/main/com/mongodb/client/internal/MongoClusterImpl.java

@@ -78,6 +78,7 @@
 import static com.mongodb.assertions.Assertions.isTrueArgument;
 import static com.mongodb.assertions.Assertions.notNull;
 import static com.mongodb.internal.TimeoutContext.createTimeoutContext;
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
 
 final class MongoClusterImpl implements MongoCluster {
     @Nullable
@@ -163,8 +164,9 @@ public ReadConcern getReadConcern() {
     @Override
     @Nullable
     public Long getTimeout(final TimeUnit timeUnit) {
+        notNull("timeUnit", timeUnit);
         Long timeoutMS = timeoutSettings.getTimeoutMS();
-        return timeoutMS == null ? null : timeUnit.convert(timeoutMS, TimeUnit.MILLISECONDS);
+        return timeoutMS == null ? null : timeUnit.convert(timeoutMS, MILLISECONDS);
     }
 
     @Override