Previous VTY configured range for the set of tdefs in timer xua didn't allow to pass a 0 to it, which "timer xua beat 0" should be able to accept in order to disable heartbeat procedure on the ASP. In order to fix it: * Change VTY range to minimal accepted value to 0 for the whole tdef set. * Make sure the VTY command validates and rejects user trying to set a value outside the accepted range of the specific timer. * Set .min_val=1 in SS7_ASP_XUA_T_ACK, so it can't accept value 0. According to spec, T(ack) is always expected to be set, even if the resulting timeout may be handled by LM instead of simply retransmitting the packet. * Write vty tests to validate the restrictions are followed properly in the VTY.
