use separate disk images for ryudevXXX

to avoid troubles like recent grizzly-after-folsom build failures.
tweak code to leave "nova console-log" outputs in the log
Merge pull request #4 from yamada-h/fix-typo

doc/setup.txt: fix URL typo
Merge pull request #3 from yamt/yamt

misc changes i'm using in my environment
run.sh: use unix socket for VNC of VMs

If other VMs are running on same host,
it may fail to bind vnc TCP port such as ":1".