Add failsafe logger for zones

Tested:
...
Nov 23 21:40:06 tmddp10-nfd01.prod.google.com swampd[4893]:
Zone `0` is in failsafe mode.
With update at `fleeting0`: The sensor has bad readings.
Nov 23 21:40:06 tmddp10-nfd01.prod.google.com swampd[4893]:
Zone `1` is in failsafe mode.
With update at `fleeting1`: The sensor has bad readings.
Nov 23 21:40:06 tmddp10-nfd01.prod.google.com swampd[4893]:
Zone `1` leaves failsafe mode.
With update at `hotswap_in_Input_Power`: The sensor has recovered.
Nov 23 21:40:06 tmddp10-nfd01.prod.google.com swampd[4893]:
Zone `0` leaves failsafe mode.
With update at `hotswap_in_Input_Power`: The sensor has recovered.
...

Change-Id: I2c296addb7ad117c03c04a27de91204796cda036
Signed-off-by: James Zheng <alphetis@google.com>
diff --git a/test/sensor_host_unittest.cpp b/test/sensor_host_unittest.cpp
index e9800cf..5e958c0 100644
--- a/test/sensor_host_unittest.cpp
+++ b/test/sensor_host_unittest.cpp
@@ -1,3 +1,6 @@
+#include "failsafeloggers/builder.hpp"
+#include "failsafeloggers/failsafe_logger.hpp"
+#include "failsafeloggers/failsafe_logger_utility.hpp"
 #include "sensors/host.hpp"
 #include "test/helpers.hpp"