Change variable and namespace name in BE (#268)

Change 'palo' to 'doris'

be/src/exprs/encryption_functions.cpp

@@ -27,7 +27,7 @@
 #include <boost/smart_ptr.hpp>
 #include "runtime/string_value.h"
 
-namespace palo {
+namespace doris {
 void EncryptionFunctions::init() {
 }