mussle: remove duplicate definition instance backup subcommand.
make shared function for volume backup task.
sta: download image from remote backup storage and extract from compressed format.
Merge branch 'master' into backup-instance-on-shared-vol
rename temp folder name function.
sta: backup volume supports compression and remote upload.
Merge branch 'master' into backup-instance-on-shared-vol
sta: add failure case process for backup volume tasks.
Merge branch 'master' into backup-instance-on-shared-vol
add missing state definition.
Merge branch 'master' into backup-instance-on-shared-vol
Merge pull request #380 from axsh/backup-instance-on-shared-vol

Deals with compressed image from sta