if install_master is true, run the state.highstate through the master 

If the vagrant file specifies install_master = true then run the state.highstate though the salt master as opposed to salt-call: `salt '*' state.highstate --verbose`

This should allow things like GitFS to be used with vagrant VMs since the salt-master is responsible for pulling those files down. When run locally though salt-call the master is bypassed.