Made changes to display a warning message when trying to do "show log alert <alert_id>" where alert id is not configured. 
While testing HA, found that it previously used "system mail from" to get the from mail id for HA log alerts and updates HA config. After the changes for "system mail from" for email alerts, ha config is not getting updated with correct mail id. Fixed this issue.

Also made a minor change in eventlog_monitor sendmail, to add a newline before "body" field to get the complete mail in all cases. Added a sig child event handler to eventlog_monitor as some sendmail child processes were becoming <defunct>.

AN(config)#sh log alert 12

Log alert 12 is not configured.

AN(config)#system mail from "ngurunathan@arraynetworks.com"
AN(config)#sh ha config

ha keepaliveip 192.168.85.132

ha vcid 2

system mail from "ngurunathan@arraynetworks.com"
AN(config)#sh system mail

system mail from "ngurunathan@arraynetworks.com"