TDengine: KILL SSMIGRATE missing authorization lets low-privilege users interrupt shared-storage migrations

TDengine is a time-series database optimized for Internet of Things devices. Prior to 3.4.1.15, TDengine Enterprise allowed an authenticated low-privilege SQL user to run KILL SSMIGRATE against an active shared-storage migration because mndProcessKillSsMigrateReq called mndKillSsMigrate while the intended MND_OPER_SSMIGRATE_DB privilege check was commented out. This issue is fixed in version 3.4.1.15.