kvm: sending std output to dev/null to prevent garbage output (#4123)

When scripts/vm/hypervisor/kvm/kvmvmactivity.sh is called with an incorrect file name, an error is printed which is then interpreted as output from the script.

When an incorrect file name is passed the script prints out:

stat: cannot stat ‘b51d7336-d964-44ee-be60-bf62783dabc’: No such file or directory
=====> DEAD <======
The KVMHAVMActivityChecker.java checkingHB() process is expecting just
=====> DEAD <======
but gets the unexpected error message and interprets the file as alive.

Author: Spaceman1984

scripts/vm/hypervisor/kvm/kvmvmactivity.sh

@@ -99,7 +99,7 @@ fi
 
 # Second check: disk activity check
 cd $MountPoint
-latestUpdateTime=$(stat -c %Y $(echo $UUIDList | sed 's/,/ /g') | sort -nr | head -1)
+latestUpdateTime=$(stat -c %Y $(echo $UUIDList | sed 's/,/ /g') 2> /dev/null | sort -nr | head -1)
 
 if [ ! -f $acFile ]; then
     echo "$SuspectTime:$latestUpdateTime:$MSTime" > $acFile