service examples: if iface do not exist, retry upping it

I've had a case of a machine where eth0 was appearing a bit later
after the boot, and appearing _downed_. ifplugd then fails to detect
"link up". Thus, depending on how service startup
("ip link set dev eth0 up") races with driver initialization,
ethernet randomly fails to initialize on boot.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

examples/var_service/supplicant_if/run

@@ -14,7 +14,7 @@ ip link set dev "$if" up || { sleep 5; exit; }
 ##echo "* Powersave disable on $if"
 ##iw dev "$if" set power_save off
 
-echo "* Starting wpa_supplicant"
+echo "* Starting wpa_supplicant on $if [$$]"
 exec \
 env - PATH="$PATH" \
 softlimit \