[Autotest][Py3] Fix pingrunner/parse_from_output

Making it more simple and moving it to a function so that it doesn't
need to be maintained in multiple spots

BUG=chromium:990593
TEST=dummy_Pass and it showed the actual ping_runner results

Change-Id: Ice6b9214fbe56580fb173c404c48696abf35af4b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2521651
Commit-Queue: Derek Beckett <dbeckett@chromium.org>
Tested-by: Derek Beckett <dbeckett@chromium.org>
Auto-Submit: Derek Beckett <dbeckett@chromium.org>
Reviewed-by: Prathmesh Prabhu <pprabhu@google.com>
diff --git a/client/common_lib/cros/network/ping_runner.py b/client/common_lib/cros/network/ping_runner.py
index 2272084..ecb6821 100644
--- a/client/common_lib/cros/network/ping_runner.py
+++ b/client/common_lib/cros/network/ping_runner.py
@@ -56,6 +56,13 @@
     return None
 
 
+def _extract_ping_loss(output):
+    for line in output.splitlines():
+        if line.find('packets transmitted') > 0:
+            return line
+    return ''
+
+
 class MacPingDelegate(object):
     """Implement ping functionality for MacOS hosts."""
 
@@ -122,8 +129,7 @@
         This function will look for both 'stdev' and 'std-dev' in test results
         to support both ping and ping6 commands.
         """
-        loss_line = ([x for x in ping_output.splitlines()
-                if x.find('packets transmitted') > 0] or [''])[0]
+        loss_line = _extract_ping_loss(ping_output)
         sent = _regex_int_from_string('([0-9]+) packets transmitted', loss_line)
         received = _regex_int_from_string('([0-9]+) packets received',
                                           loss_line)
@@ -218,8 +224,7 @@
             time 90 ms
 
         """
-        loss_line = ([x for x in ping_output.splitlines()
-                if x.find('packets transmitted') > 0] or [''])[0]
+        loss_line = _extract_ping_loss(ping_output)
         sent = _regex_int_from_string('([0-9]+) packets transmitted', loss_line)
         received = _regex_int_from_string('([0-9]+) received', loss_line)
         loss = _regex_float_from_string('([0-9]+(\.[0-9]+)?)% packet loss',