usb-nic: Improve interface start and ping default gateway

Sometimes, it takes a lot of time to setup network interface. Timeout
for interface setup was increased. There was also added debug option
to display more details. There is no need for loop before ping,
network is already setup when is ifup done. Ping peer was changed to
gateway to fully validate network functionality.

tests/kernel/usb_nic.pm

@@ -24,15 +24,11 @@ sub run {
     assert_script_run "echo \"BOOTPROTO='dhcp'\" > /etc/sysconfig/network/ifcfg-$interface";
     assert_script_run "echo \"STARTMODE='auto'\" >> /etc/sysconfig/network/ifcfg-$interface";
 
-    assert_script_run "ifup $interface";
+    assert_script_run("ifup $interface -o debug", 60);
 
-    # wait until interface is up
-    my $timeout = 20;
-    ($timeout-- && sleep 5) while (script_run "ip -4 addr show $interface | grep inet" && $timeout);
-
-    my $ping_peer = script_output "ip route show dev $interface | cut -d ' ' -f 7";
-    assert_script_run "ping -I $interface -c 4 $ping_peer";
-    assert_script_run "ifdown $interface";
+    my $route = script_output "ip route show default";
+    my @ping_peer = $route =~ /default via (\S+)/;
+    assert_script_run "ping -I $interface -c 4 @ping_peer";
 }
 
 sub test_flags {