public static VersionedObjectList execute(ExecutablePool pool, String region, List keys,
      Object callback) {
    AbstractOp op = new GetAllOpImpl(region, keys, callback);
    op.initMessagePart();
    return ((VersionedObjectList) pool.execute(op)).setKeys(keys);
  }
Does a region getAll on a server using connections from the given pool to communicate with the
server.

@param pool the pool to use to communicate with the server.
@param region the name of the region to do the getAll on
@param keys list of keys to get
@return the map of values found by the getAll if any
geode-core/src/main/java/org/apache/geode/cache/client/internal/GetAllOp.java