Some interfaces (typically from docker or virtual machines) were added
in the candidates even if down. For example:

9: br-b8251442502e: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue
state DOWN group default

Even if state=DOWN if_enum_by_af consider the ip as valid and adds it in the
candidates because IFF_UP is true. However, if_enum_by_af should use IFF_RUNNING
to detect if the interface is up and running before adding it. Like
 iproute2/bridge/link.c does for print_link_flags.

Resource: https://man7.org/linux/man-pages/man7/netdevice.7.html

Upstream ticket: https://github.com/pjsip/pjproject/issues/2686
Change-Id: I168954509ec935bb45e39700e57a0c12ac837931
GitLab: #495