faft: Fix forever waiting for sshing the non-existing 'local' target

The previous CL broke FAFT.
  https://gerrit.chromium.org/gerrit/37944

As the default target_host is 'local'. It makes the test forever waiting
for sshing the non-existing 'local'.

This CL is to change its default value to None. If None, skip the connection
and not do power cycle.

BUG=chrome-os-partner:13970
TEST=Run a FAFT test on Link and passed.

Change-Id: I533cf79c5a3075c410741f5b5c586cf574723b5a
Reviewed-on: https://gerrit.chromium.org/gerrit/38366
Reviewed-by: Gediminas Ramanauskas <gedis@chromium.org>
Commit-Ready: 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 9ae4656..6121e9e 100644
--- a/server/cros/faftsequence.py
+++ b/server/cros/faftsequence.py
@@ -176,7 +176,10 @@
             # Setting up key matrix mapping
             self.servo.set_key_matrix(self.client_attr.key_matrix_layout)
 
-            self._host = hosts.create_host(self.servo.get_target_hostname())
+            self._host = None
+            if (self.client_attr.broken_rec_mode and
+                    self.servo.get_target_hostname()):
+                self._host = hosts.create_host(self.servo.get_target_hostname())
 
 
     def setup(self, ec_wp=None):
@@ -948,7 +951,7 @@
             self.ec.set_hostevent(chrome_ec.HOSTEVENT_KEYBOARD_RECOVERY)
             self.servo.power_short_press()
         elif self.client_attr.broken_rec_mode:
-            if self._host.has_power():
+            if self._host and self._host.has_power():
                 self._host.power_cycle()
             else:
                 logging.info('You have %d seconds to power cycle this device.',