[Features] Develop mode for scripts debugging

[free6om]

there are lots of features need configured shell scripts to work well: role probe, member join and leave in RSM, backup related scripts etc. .
running scripts is not a bad thing, but it is painful to setup the environment and debug the scripts.
KB should provide a Develop Mode to setup the script debug environment automatically to ease the pain.

[free6om]

mirrord just can do what this feature wants, and it's a more general way. will close this feature request and suggest using mirrord instead.