Make dev.sh pulldb save db.dump into /tmp

[alexgleason]

Just ran into an issue where a previously-created db.dump was actually not owned by the current user. This would happen if you were to, eg, run sudo ./dev.sh pulldb where db.dump would be owned by root instead.

If we store db.dump into /tmp instead we can give it a somewhat randomized temporary name and let the system clean it up. This seems more appropriate and will prevent permission bugs like this.