[Labs-l] Instance scheduler modified, could cause instance creation to fail

[Ryan Lane]

I've switched from using the chance scheduler to the simple scheduler
for nova (https://gerrit.wikimedia.org/r/#change,2731). This means
that when instances are created, the compute node with the least
number of instances running will be chosen, rather than before where
any random compute node was chosen.

The new scheduler has some options which limit which nodes are chosen,
though, and the defaults may be set a little low. If you create an
instance and it stays in the scheduling or pending mode forever (or it
eventually fails), let me know and I'll tweak the configuration
options.

- Ryan