Session cleanup for db.security_group_rule_* methods

Session objects shouldn't be used in public db.api methods
because db.api should be independent of db implementation.

Remove session parameter from:
test_security_group_rule_destroy
test_security_group_rule_get
test_security_group_rule_get_by_security_group
test_security_group_rule_get_by_security_group_grantee

blueprint db-session-cleanupRoutine refactor.

Change-Id: I36a71547124b655ed89d340fed02315f3b7f1530
Merge "Session cleanup for db.security_group_rule_* methods"