Fix usage of SQLAlchemy Query.first() method
Fix usage of SQLAlchemy Query.first() method

Query.first() doesn't raise the NoResultFound exception
if no result is found but rather returns None, so wrapping
of Query.first() call into a try/except NoResultFound block
is useless.

Fixes bug 1177842.

Change-Id: I0bd0e6d8299734b485dd1a1ac36bf6c295fd8932

gkotton/vmware-nsx,gkotton/vmware-nsx