[gt-user] a minor correction in the docs

[Amitav Mohanty]

Hello

In the quickstart page for the Globus toolkit, while setting up the second
machine as line says

source $GLOBUS_LOCATION/globus-user-env.sh

I think it should be changed to source
$GLOBUS_LOCATION/etc/globus-user-env.sh

Regards
Amitav