[fast/warm-reboot] Put ERR message in syslog when a failure is seen (s…

…onic-net#3186)

MSFT ADO: 26918588

This change is to add ERR logs generated during warm-reboot script to syslog.
Currently the ERR logs are sent in stdout and a corresponding entry is not added to syslog.
This makes it difficult to debug issues when stdout is not readily available.

How I did it
Modified existing error function to add the log entry to syslog.

How to verify it
Verified manually on physical device

scripts/fast-reboot

@@ -54,6 +54,7 @@ EXIT_TEAMD_RETRY_COUNT_FAILURE=23
 function error()
 {
     echo $@ >&2
+    logger -p user.err "Error seen during warm-reboot shutdown process: $@"
 }
 
 function debug()