tools: Make use of the correct environment variables

tools: Make use of the correct environment variables

Since commit 834c5720 which extracted the generic functionality out of virsh
and made it available for other clients like virt-admin to make use of it, it
also introduced a bug when it renamed the original VIRSH_ environment variables
to VSH_ variables. Virt-admin of course suffers from the same bug, so this
patch modifies the generic module vsh.c to construct the correct name for
environment variables of each client from information it has.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1357363

Signed-off-by: Erik Skultety <eskultet@redhat.com>