Previously on new subunit2sql releases we would automatically run the
db upgrade command to cover any potential db migrations added in the
new release. However if there is a potential issue with a new migration
this could potentially corrupt the db. So to offset this risk this
commit runs a mysqldump to backup the db before we run the migration
command so in case things go bad we can restore the db from the backup.
Change-Id: I65d300699c457aeb4ead86c08077f7495eb24ed4
afc25cba89