removal of /var/lib/cassandra in contrail-openstack-database postinst is done only on install and not on upgrade

Conflicts:

	common/debian/contrail-openstack-database/debian/contrail-openstack-database.postinst

Change-Id: Ic6ce221d31b470213951f89d5256874abd4553fc
Merge "removal of /var/lib/cassandra in contrail-openstack-database postinst is done only on install and not on upgrade"