Change variable and namespace name in BE (#268)

Change 'palo' to 'doris'

be/src/runtime/buffered_tuple_stream.cpp

@@ -28,7 +28,7 @@
 #include "util/pretty_printer.h"
 #include "common/status.h"
 
-namespace palo {
+namespace doris {
 //using namespace strings;
 
 // The first NUM_SMALL_BLOCKS of the tuple stream are made of blocks less than the