Provide ability to configure keystone resync interval

Contrail API provides an option 'keystone_resync_interval_secs'.
Its default value of 60sec is not always convenient.
This commit introduces support of this param in formula.

Change-Id: I43bff19d4120fe86759efb56f28afc64e44e2d91
Related-PROD: PROD-27794
2 files changed