Fix bug 1001: RO can't find datacenter on HA

- Fix get_vim_thread() function to check if the thread exists. If not, create it.
- Add worker_id global parameter
- Add get_process_id() function
- Simplify get_non_used_vim_name() function

Change-Id: I10b3426af79df89688ae4b75caf395a6c238fba0
Signed-off-by: David Garcia <david.garcia@canonical.com>