acm/acme.c: Fix path records comparison

In case of verifying cached path record vs. path record
received from SA, compare only the relevant bits
(for rate & mtu those are 6 lsb bits).

Pointed out by Lenny Verkhovsky <lennyb@mellanox.com>,
during Kodiak cluster integration.

Signed-off-by: Ilya Nelkenbaum <ilyan@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>