Host scheduler refactoring. Move HostScheduler out of monitor_db.

Host scheduler refactoring. Move HostScheduler out of monitor_db.

In order to facilitate site extensibility of HostScheduler we need to factor out the dependence on global variables in monitor_db. I modeled this refactoring off of monitor_db_cleanup.

The main changes I've made are as follows:
1. Move BaseHostScheduler, site import, and SchedulerError out of monitor_db. SchedulerError must be moved to prevent a cyclical dependency.
2. Convert staticmethod/classmethods in BaseHostScheduler, to normal methods.
3. Fix unit tests and monitor_db to import SchedulerError from host_scheduler.

Change-Id: I0c10b79e70064b73121bbb347bb71ba15e0353d1

BUG=chromium-os:12654
TEST=Ran unit tests. Tested with private Autotest instance.

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=aa51336

[ericli, 2011-02-28 22:41:16]

LGTM with nit.

http://codereview.chromium.org/6597047/diff/6/scheduler/host_scheduler.py
File scheduler/host_scheduler.py (right):

http://codereview.chromium.org/6597047/diff/6/scheduler/host_scheduler.py#new...
scheduler/host_scheduler.py:23: class
base_host_scheduler(metahost_scheduler.HostSchedulingUtility):
ClassName uppercase.

[DaleCurtis, 2011-03-01 00:25:36]

http://codereview.chromium.org/6597047/diff/6/scheduler/host_scheduler.py
File scheduler/host_scheduler.py (right):

http://codereview.chromium.org/6597047/diff/6/scheduler/host_scheduler.py#new...
scheduler/host_scheduler.py:23: class
base_host_scheduler(metahost_scheduler.HostSchedulingUtility):
On 2011/02/28 22:41:16, ericli wrote:
> ClassName uppercase.

Done.