psu-ng: Fix log error for missing PSU

Fixed missing PSU log error during power on. The issue was replicated
as follow:
1 - Chassis powered off
2 - Remove power cable from PSUx
3 - Remove PSUx from the carrier
4 - Power on chassis

Expect to see error log entry for missing PSUx. Fixed validateConfig to
only restart validationTimeout when there is a input fault and PSU
present or VINUVFault and PSU present.

Test:
  1 - System at standby
     a - Removed PSU0
     b - Reset BMC
     c - Power on chassis
     d - Verified error logged
  2 - System at standby
     a - Pull PSU cable
     b - Wait 10 seconds
     d - Remove PSU and power on the chassis
     d - Verified error logged
  3 - System at standby
     a - Remove power cord from PSU
     b - Chassis power on
     c - Verified an error is logged

Change-Id: Ife099d2d4871cb5905e4e382180b6b8cce97c66d
Signed-off-by: Faisal Awada <faisal@us.ibm.com>
diff --git a/phosphor-power-supply/psu_manager.cpp b/phosphor-power-supply/psu_manager.cpp
index 44827ee..2832959 100644
--- a/phosphor-power-supply/psu_manager.cpp
+++ b/phosphor-power-supply/psu_manager.cpp
@@ -978,7 +978,7 @@
 
     for (const auto& psu : psus)
     {
-        if ((psu->hasInputFault() || psu->hasVINUVFault()))
+        if ((psu->hasInputFault() || psu->hasVINUVFault()) && psu->isPresent())
         {
             // Do not try to validate if input voltage fault present.
             validationTimer->restartOnce(validationTimeout);