Add option for daemon to continue running after timeout

Added new command line option that lets someone disable the
watchdog timer on timer expiration instead of the default
action of it exiting.

Change-Id: I1c3414d4378872860ac083836cda4809fa26237a
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/watchdog.cpp b/watchdog.cpp
index de90567..0c93d31 100644
--- a/watchdog.cpp
+++ b/watchdog.cpp
@@ -36,6 +36,7 @@
         else
         {
             timer.setEnabled<std::false_type>();
+            timer.clearExpired();
             log<level::INFO>("watchdog: disabled");
         }
     }