avoid write dump result to stdout

[trim21]

I'm tring to dump mysql to s3 and I find it write entire content of sql (output of mysqldump) to stdout, make it hard to find out what's happening

[trim21]

I find the DumpName is not actually used in the mysql/Dump, but it's expected to write output to it, is this a bug?

docker-backup-database/pkg/dbdump/mysql/mysql.go

Line 18 in dd44d09

DumpName string