tools: bootstrap_web.sh: Fix "/usr/bin/env: node: No such file or directory" error.
tools: bootstrap_web.sh: Fix "/usr/bin/env: node: No such file or directory" error.

After node is freshly installed, it is not part of PATH. By sourcing
dev.env, we fix this.

I've also changed the file of the temporary, downloaded file to include ".tar".

tinyspeck/vitess,alainjobart/vitess,tinyspeck/vitess,mattharden/vitess,applift/vitess,dcadevil/vitess,pivanof/vitess,rnavarro/vitess,enisoc/vitess,applift/vitess,vitessio/vitess,mahak/vitess,dcadevil/vitess,davygeek/vitess,dcadevil/vitess,sougou/vitess,mattharden/vitess,sougou/vitess,mattharden/vitess,tirsen/vitess,tirsen/vitess,tirsen/vitess,mattharden/vitess,vitessio/vitess,applift/vitess,applift/vitess,applift/vitess,mahak/vitess,rnavarro/vitess,vitessio/vitess,HubSpot/vitess,rnavarro/vitess,sougou/vitess,davygeek/vitess,pivanof/vitess,vitessio/vitess,HubSpot/vitess,applift/vitess,davygeek/vitess,pivanof/vitess,tirsen/vitess,pivanof/vitess,enisoc/vitess,davygeek/vitess,applift/vitess,alainjobart/vitess,dcadevil/vitess,mattharden/vitess,alainjobart/vitess,vitessio/vitess,rnavarro/vitess,mahak/vitess,rnavarro/vitess,tinyspeck/vitess,tirsen/vitess,davygeek/vitess,alainjobart/vitess,davygeek/vitess,tinyspeck/vitess,sougou/vitess,sougou/vitess,mattharden/vitess,sougou/vitess,dcadevil/vitess,pivanof/vitess,tirsen/vitess,tirsen/vitess,vitessio/vitess,HubSpot/vitess,mattharden/vitess,alainjobart/vitess,enisoc/vitess,davygeek/vitess,tinyspeck/vitess,mattharden/vitess,pivanof/vitess,mahak/vitess,sougou/vitess,rnavarro/vitess,tirsen/vitess,mahak/vitess,enisoc/vitess,alainjobart/vitess,HubSpot/vitess,vitessio/vitess,pivanof/vitess,alainjobart/vitess,rnavarro/vitess,alainjobart/vitess,enisoc/vitess,mahak/vitess,mattharden/vitess,dcadevil/vitess,enisoc/vitess,applift/vitess,HubSpot/vitess,rnavarro/vitess,applift/vitess,applift/vitess,vitessio/vitess,HubSpot/vitess,HubSpot/vitess,pivanof/vitess,rnavarro/vitess,sougou/vitess,mahak/vitess,enisoc/vitess,dcadevil/vitess,pivanof/vitess,tinyspeck/vitess,mahak/vitess,tirsen/vitess,mattharden/vitess,tinyspeck/vitess,HubSpot/vitess