print zone failsafe reason when enter failsafe mode

Tested:
```
Jun 24 01:52:45 bmc sel-logger[640]: cpu0_nbm critical high threshold assert. Reading=49.000000 Threshold=45.000000.
Jun 24 01:52:46 bmc swampd[2944]: Zone 2 fans, entering failsafe mode, output pwm: 100
Jun 24 01:52:46 bmc swampd[2944]: Fail sensor: cpu0_nbm, reason: Sensor threshold asserted
Jun 24 01:52:46 bmc swampd[2944]: Zone 0 fans, entering failsafe mode, output pwm: 100
Jun 24 01:52:46 bmc swampd[2944]: Fail sensor: cpu0_nbm, reason: Sensor threshold asserted
```

Signed-off-by: Harvey Wu <Harvey.Wu@quantatw.com>
Change-Id: I607d01b6bed11b00a40153db6521a9c9d23da519
diff --git a/pid/fancontroller.cpp b/pid/fancontroller.cpp
index 378ef9b..11538be 100644
--- a/pid/fancontroller.cpp
+++ b/pid/fancontroller.cpp
@@ -176,6 +176,14 @@
                           << (failsafeCurrState ? "entering failsafe"
                                                 : "returning to normal")
                           << " mode, output pwm: " << percent << "\n";
+
+                std::map<std::string, std::pair<std::string, double>>
+                    failSensorList = _owner->getFailSafeSensors();
+                for (const auto& it : failSensorList)
+                {
+                    std::cerr << "Fail sensor: " << it.first
+                              << ", reason: " << it.second.first << "\n";
+                }
             }
         }
     }