ciao-down: Update Go to 1.8
ciao-down: Update Go to 1.8

This commit updates the version of Go used in ciao-down ciao VMs from
1.7.4 to 1.8.  The version used in the creation of clearcontainer vms
has not been changed.

Signed-off-by: Mark Ryan <f16215f7acd0bd7fdc465539215bd574c785b062@intel.com>

mcastelino/ciao,erick0z/ciao,matthewrsj/ciao,ciao-project/ciao,01org/ciao,erick0z/ciao,mcastelino/ciao,obedmr/ciao,markdryan/ciao,matthewrsj/ciao,matthewrsj/ciao,rbradford/ciao,kaccardi/ciao,01org/ciao,mrkz/ciao,erick0z/ciao,mcastelino/ciao,obedmr/ciao,rbradford/ciao,markdryan/ciao,obedmr/ciao,tpepper/ciao,kaccardi/ciao,tpepper/ciao,mrkz/ciao,mrkz/ciao,tpepper/ciao,ciao-project/ciao