faft: Increase timeout of waiting DUT sshable to 3 minutes

Jetsteam devices take longer time than others to initialize network interfaces
and start sshd. Increase the timeout to 3 minutes to solve this issue. It
doesn't affect other devices on normal test cases.

BUG=chrome-os-partner:34513
TEST=Ran firmware_DevMode on Whirlwind passed.

Change-Id: Ibe5b3a36ccd29046ca2f3c4caab07e5767a99579
Reviewed-on: https://chromium-review.googlesource.com/283130
Tested-by: Wai-Hong Tam <waihong@chromium.org>
Reviewed-by: Yusuf Mohsinally <mohsinally@chromium.org>
Commit-Queue: Wai-Hong Tam <waihong@chromium.org>
diff --git a/server/cros/faft/firmware_test.py b/server/cros/faft/firmware_test.py
index e0198eb..bafc1e1 100644
--- a/server/cros/faft/firmware_test.py
+++ b/server/cros/faft/firmware_test.py
@@ -42,7 +42,7 @@
         self.faft_client = RPCProxy(host)
         self.lockfile = '/var/tmp/faft/lock'
 
-    def wait_for_client(self, timeout=100):
+    def wait_for_client(self, timeout=180):
         """Wait for the client to come back online.
 
         New remote processes will be launched if their used flags are enabled.