[Fix](load) Fix uninitiated load_type (not a valid value for type) of…

… StreamLoadContext when operate_txn_2pc (apache#38033)

/root/doris/be/src/runtime/stream_load/stream_load_executor.cpp:384:14:
runtime error: load of value 3200171710, which is not a valid value for
type 'TLoadType::type'
#0 0x55be4e2cf808 in
doris::StreamLoadExecutor::collect_load_stat(doris::StreamLoadContext*,
doris::TTxnCommitAttachment*)
/root/doris/be/src/runtime/stream_load/stream_load_executor.cpp:384:14
#1 0x55be4e2d2666 in
doris::StreamLoadExecutor::rollback_txn(doris::StreamLoadContext*)
/root/doris/be/src/runtime/stream_load/stream_load_executor.cpp:364:9
#2 0x55be80413748 in
doris::CloudStreamLoadExecutor::operate_txn_2pc(doris::StreamLoadContext*)
/root/doris/be/src/cloud/cloud_stream_load_executor.cpp:80:33
#3 0x55be50cad893 in
doris::StreamLoad2PCAction::handle(doris::HttpRequest*)
/root/doris/be/src/http/action/stream_load_2pc.cpp:85:49

be/src/runtime/stream_load/stream_load_context.h

@@ -123,7 +123,7 @@ class StreamLoadContext {
 public:
     static const int default_txn_id = -1;
     // load type, eg: ROUTINE LOAD/MANUAL LOAD
-    TLoadType::type load_type;
+    TLoadType::type load_type = TLoadType::type::MANUL_LOAD;
     // load data source: eg: KAFKA/RAW
     TLoadSourceType::type load_src_type;