revalidator: Simplify push_dump_ops__().

Commit acaa8dac49 (revalidator: Eliminate duplicate flow handling.)
ensured that a ukey will always exist for a given flow, even if it is
about to be deleted. This means that push_dump_ops__() no longer needs
to handle the case where there is no ukey. This commit removes the
redundant code.

Signed-off-by: Joe Stringer <joestringer@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>