Remove annoying be log "cancel fragment"

[murphyatwork]

Enhancement

When executing a query with a LIMIT clause, such as SELECT * FROM tbl WHERE k1 = 1 LIMIT 1, the be.INFO log consistently records an entry.

This logging is unnecessary and distracting because the LIMIT 1 clause uses short-circuit logic. Once a single row is returned, all running fragments are canceled, making the cancellation a normal and expected behavior.

The primary purpose of this logging is to record exceptions for debugging when a fragment is canceled due to an exception. Therefore, we should check the cancellation reason—if it's a normal cancellation, no log should be printed.

I20251209 06:44:51.835576 254010889339072 internal_service.cpp:532] cancel fragment, fragment_instance_id=9051afd0-d4ca-11f0-a523-0a462c2cbf2b, reason: QueryFinished

version: all versions