MySqlDatabase: remove member errorAlreadyTriggered
MySqlDatabase: remove member errorAlreadyTriggered

This member variable is no longer used. Its purpose was to
prevent recursive errors if an error was thrown while reporting
a database error, which became unnecessary in c544e1335dd97bb.

smrealms/smr,hemberger/smr,hemberger/smr,smrealms/smr,hemberger/smr,hemberger/smr,smrealms/smr