create_db_entry_for_new_instance did not call sgh for default
create_db_entry_for_new_instance did not call sgh for default

When an instance is launched create_db_entry_for_new_instance() is
called which calls self.db.instance_create(). Then,
db.security_group_ensure_default() is called which creates the
default security group entry in the nova db. Though the sgh handler was
not called. Alternatively, if any nova secgroup-* call is made the sgh
is called which creates the default security group. This patch adds
a call to ensure_default() before db.instance_create() so the sgh
is called. Fixes a case missed in  bug 1050982

Change-Id: I9649b5ef026ca18a55abfb66e87fd0e358eba6f2

paulmathews/nova,paulmathews/nova,paulmathews/nova