CA-116160: Python exception in HBA SR create.

len() on dictionary iterkeys is not valid in Python 2.6.
Replaced it with len() directly on the dictionary.

Signed-off-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Reviewed-by: Vineeth Thampi Raveendran <vineeth.thampi@citrix.com>

GitHub: closes #47 on xapi-project/sm