VPNaaS datamodel IKEPolicy lifetime unit typo

There was a typo in handling the IKEPolicy
lifetime, during the IKEPolicy creation time.

-Fixed the typo issue

Fixes bug 1207572

Change-Id: If8c56619c9a340a04e336b6b83d219df10b91e6c
Merge "VPNaaS datamodel IKEPolicy lifetime unit typo"