Moved security rules and keypair creation into init first.
Launch script now takes image name as positional argument, and name of
instance as a named argument. This makes it work more like launch in
other Canonical tools.
Written in Python, for ease of maintenance.
--retry and --wait args allow it to behave like tests expect it to,
while humans will get a much more intuitive (and much less noisy)
Also increased time we wait for a ping on the host, to allow for
slower, pure qemu, emulation times, and bring it in line with what
Tempest does in similar situations.