virt test: ping: Increase timeout of ping external host

The timeout for ping to external host is a bit small,
we can't get the ping summary at last.

>From ping output below (snapped from a windows guest),
ping program will wait about 4s for every packet.
We'd better to set the timeout value to 10 * (4 + 1) = 50s
for windows guest at least.

C:\> ping someserver -n 10 -l 65500
2012-12-28 13:44:02: Pinging someserver [1.1.1.1] with 65500 bytes of data:
2012-12-28 13:44:02: Reply from 1.1.1.1: bytes=65500 time=3ms TTL=63
2012-12-28 13:44:07: Request timed out.
2012-12-28 13:44:08: Reply from 1.1.1.1: bytes=65500 time=6ms TTL=63
2012-12-28 13:44:09: Reply from 1.1.1.1: bytes=65500 time=6ms TTL=63
2012-12-28 13:44:10: Reply from 1.1.1.1: bytes=65500 time=6ms TTL=63
2012-12-28 13:44:15: Request timed out.
2012-12-28 13:44:16: Reply from 1.1.1.1: bytes=65500 time=6ms TTL=63
2012-12-28 13:44:21: Request timed out.
2012-12-28 13:44:22: Reply from 1.1.1.1: bytes=65500 time=6ms TTL=63
2012-12-28 13:44:22: (Process terminated with status 0)

This patch increases the timeout to 60s, to make us can
get a meaningful result except for a ShellTimeoutError.
Signed-off-by: NQingtang Zhou <qzhou@redhat.com>
Acked-by: NXu Tian <xutian@redhat.com>

tests/ping.py

@@ -112,7 +112,7 @@ def run_ping(test, params, env):
                     error.context("Ping with packet size %s" % size,
                                   logging.info)
                     status, output = session.cmd_status_output(cmd % size,
-                                                               timeout=20)
+                                                               timeout=60)
                     _get_loss_ratio(output)
 
                     if status != 0: