Vagrantfile: make a few small changes & fixes
Vagrantfile: make a few small changes & fixes

This commit makes the following changes:
- changes some messages to say exactly what's being done
- adds support for vagrant-cachier
- enables kvm paravirt
- bumps Go to 1.9.3

rastislavszabo/vpp,brecode/vpp,milanlenco/vpp-1,brecode/vpp,milanlenco/vpp-1,brecode/vpp,rastislavszabo/vpp,rastislavszabo/vpp,rastislavszabo/vpp,milanlenco/vpp-1,rastislavszabo/vpp,brecode/vpp,brecode/vpp,rastislavszabo/vpp,milanlenco/vpp-1,rastislavszabo/vpp,milanlenco/vpp-1