Fixed OS-98 (setting hostname upon launch)

_copy_instance now sets the hostname to new_name. This means that when an instance is launched or blessed, its hostname will be set to its display_name.

Change-Id: I304b4509e1ad771f792088813ffc9cf32bfa2a69
Merge branch 'stable/essex' into stable/folsom

Change-Id: I238166f5900e3995a1b570a85697619c2b226889