Adding sysstat monitoring

You can add sysstat logging on the devstack run.
In CI environemnt, sometimes VM creation, Volume creation or
Python unit testing timeouts. It is valuable to monitor
sysstat for investigate the issues.

- How to enable sysstat ( Default is off )
enable_service sysstat

- This commit adds two env variables.
SYSSTAT_FILE : sysstat log file
SYSSTAT_DURATION : duration of sysstat monitoring

Change-Id: I65efb574ef141e6e78c69218f4327df59b3258e2
Fix aggregates exercise

Fixes bug 1131244

aggregates.sh was making assumptions on the working directory. Thus it
failed, if the current working directory is not devstack. This pathch
makes the sourcing to use the full path for openrc.

Change-Id: I10c83c88112ead97b43873e1034b0e76e4f889f4
Merge "Fix aggregates exercise"
Merge "Adding sysstat monitoring"