NSX: Remove unneed call to _ensure_default_security_group

This patch removes an unneeded call to _ensure_default_security_group
which does not need to be called in create_security_group_rule_bulk()
as one would need to call get_security_groups() to look up the uuid
of the default security group which be would created it for us, BOOM!

Change-Id: I628a94c7ea9553dcefa68fa956f25244f0abbb18
Closes-bug: 1340536
Merge "NSX: Remove unneed call to _ensure_default_security_group"