faft: Skip checking test image in USB when servod runs in a different host

When servod runs in a different host, the original check doesn't work since
we can't access the servo host. Skip the check temporarily such that it won't
break the tests. Should find a way to work-around it.

BUG=chromium-os:34395
TEST=manual, run the following test using Beaglebone:
$ run_remote_tests.sh --board daisy --remote dut \
                      --args "servo_host=dut-servo" RecoveryButton/control$

Change-Id: Ib0c44ca6eec4d17e00d4f85f3c54bd3b5efdf870
Reviewed-on: https://gerrit.chromium.org/gerrit/36211
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
Reviewed-by: Tom Wai-Hong Tam <waihong@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
diff --git a/server/cros/faftsequence.py b/server/cros/faftsequence.py
index a3c8e69..abf1c02 100644
--- a/server/cros/faftsequence.py
+++ b/server/cros/faftsequence.py
@@ -323,6 +323,14 @@
         Raises:
           error.TestError: if USB disk not detected or not a test image.
         """
+        # TODO(waihong@chromium.org): We skip the check when servod runs in
+        # a different host since no easy way to access the servo host so far.
+        # Should find a way to work-around it.
+        if not self.servo.is_localhost():
+            logging.info('Skip checking Chrome OS test image in USB as servod '
+                         'runs in a different host.')
+            return
+
         if usb_dev:
             assert self.servo.get('usb_mux_sel1') == 'servo_sees_usbkey'
         else: