Use IFNAME= prefix for global UDP control interface events

Use IFNAME= prefix for global UDP control interface events

There does not seem to be a good reason for using the different IFACE=
prefix on the UDP control interface. This got added when the UDP
interface in wpa_supplicant was extended in commit f0e5d3b5c6c7
("wpa_supplicant: Share attach/detach/send UDP ctrl_iface functions")
and that was then extended to hostapd in commit e9208056856c ("hostapd:
Extend global control interface notifications").

Replace the IFACE= prefix in UDP case with IFNAME= to be consistent with
the UNIX domain socket based control interface.

This fixes a problem when at least one test case fail (hapd_ctrl_sta)
when remote/udp used. This also fixes test_connectivity().

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@gmail.com>