Revert "Make nova-network use conductor for security groups refresh"

This reverts commit b1838c258df2465756e551fdb879b1d4a748cb2b.

This makes network manager issue security group refresh calls directly
instead of going through conductor now that the compute api call is
converted to objects.

Related to blueprint kilo-objects

Change-Id: I74e002384b11063e30450e3854a95b6b848ddfb6
Remove unused db.security_group_rule_get_by_security_group_grantee()

Change-Id: I968cab433f8158e8b1ee1eecb075396cc2d55a07