Update the default CIRROS_VERSION to 0.3.4, which has better support
for IPv6 and some other bugfixes.
Co-Authored-By: Scott Moser <smoser@ubuntu.com>
Change-Id: I03ee6e1403680fb6c421225a7cadaf8a82edf702
Depends-On: Iac9f108d947ff4a51f99c6e8ad9d1ac5b32c000a