[moblab] Extend the connect SSH timout by 1 second.

The UI tried to identify the devices that can be added to moblab
by SSH onto them, the timeout seems to be too short now, extend.

Also updated the unit test

BUG=chromium:990418
TEST=local moblab testing.

Change-Id: Ie8fa2f15127902fd8531c2715d176b71f65fedbe
Reviewed-on: https://chromium-review.googlesource.com/1733691
Tested-by: Keith Haddow <[email protected]>
Commit-Ready: ChromeOS CL Exonerator Bot <[email protected]>
Legacy-Commit-Queue: Commit Bot <[email protected]>
Reviewed-by: Keith Haddow <[email protected]>
Reviewed-by: Aviv Keshet <[email protected]>
Reviewed-by: Prathmesh Prabhu <[email protected]>
diff --git a/frontend/afe/moblab_rpc_interface.py b/frontend/afe/moblab_rpc_interface.py
index f04379d..ed0624c 100644
--- a/frontend/afe/moblab_rpc_interface.py
+++ b/frontend/afe/moblab_rpc_interface.py
@@ -640,7 +640,7 @@
 
     @return: True if the ssh connection is good False else
     """
-    cmd = ('ssh -o ConnectTimeout=2 -o StrictHostKeyChecking=no '
+    cmd = ('ssh -o ConnectTimeout=3 -o StrictHostKeyChecking=no '
             "root@%s 'timeout 2 cat /etc/lsb-release'") % ip
     try:
         release = subprocess.check_output(cmd, shell=True)