Add 'schedule' to session schema
Add 'schedule' to session schema

Currently we can create a new session with json
file that has no 'schedule' option successfully,
but when we add a new job to the session, it will
be failed with internal error. This patch add
'schedule' validation in session creating.

Change-Id: Ib092700d8d08d79a4708947eaad86ec48c24b4a9
Closes-Bug: #1679998

szaher/freezer-api,szaher/freezer-api,openstack/freezer-api,openstack/freezer-api,openstack/freezer-api,openstack/freezer-api,szaher/freezer-api,szaher/freezer-api