!4684 修复drop directory if exists 在匿名块中执行报错，与直接在vsql的结果不一致

Merge pull request !4684 from 小海獭/dropDir_msg_inconsistent

src/common/backend/nodes/copyfuncs.cpp

@@ -6681,6 +6681,7 @@ static DropDirectoryStmt* _copyDropDirectoryStmt(const DropDirectoryStmt* from)
     DropDirectoryStmt* newnode = makeNode(DropDirectoryStmt);
 
     COPY_STRING_FIELD(directoryname);
+    COPY_SCALAR_FIELD(missing_ok);
 
     return newnode;
 }

src/common/backend/nodes/equalfuncs.cpp

@@ -3133,6 +3133,7 @@ static bool _equalCreateDirectoryStmt(const CreateDirectoryStmt* a, const Create
 static bool _equalDropDirectoryStmt(const DropDirectoryStmt* a, const DropDirectoryStmt* b)
 {
     COMPARE_STRING_FIELD(directoryname);
+    COMPARE_SCALAR_FIELD(missing_ok);
 
     return true;
 }