jstests/replsets/localhostAuthBypass.js fails in disagg_replica_sets in runNonlocalTest(), which times out connecting to the primary through the address from get_ipaddr() (e.g. 192.168.160.1:20428). The mongod is listening on 0.0.0.0.

Cause: get_ipaddr() in jstests/libs/network/host_ipaddr.js takes the first non-loopback inet address from ifconfig/ip addr. Interfaces are listed by name, so docker bridges (br-*, docker0) come before the host NIC. In disagg suites, every DisaggReplSetTest creates and removes its own SLS docker-compose network. So the helper can return a bridge address that is no longer reachable by the time the test connects to it.

Fix: Make get_ipaddr() use the source address of the default route first (ip -4 route get 1.1.1.1), and keep the existing interface-listing chain as a fallback. This also covers the other tests that use get_ipaddr().