Changed setGetTableFunction() to be a noop if tables is already set.

Author: Norman Jordan

src/main/java/software/amazon/documentdb/jdbc/metadata/DocumentDbSchema.java

@@ -133,7 +133,9 @@ public void setGetTableFunction(
             @NonNull final Function<String, DocumentDbSchemaTable> getTableFunction,
             @NonNull final Function<Set<String>, Map<String, DocumentDbSchemaTable>> getRemainingTablesFunction)
             throws IllegalStateException {
-        if (this.tables != null || this.tableReferences == null) {
+        if (this.tables != null) {
+            return;
+        } else if (this.tableReferences == null) {
             throw new IllegalStateException(
                     SqlError.lookup(SqlError.INVALID_STATE_SET_TABLE_FUNCTION));
         }