Added host validation.

check-cert.sh

 #!/bin/sh
 fqdn=$1
+port=${2:-443}
 [ -x $fqdn ] && echo "FQDN of the site is required." && exit 1
-echo "" | openssl s_client -servername $fqdn -connect $fqdn:443 2>/dev/null | openssl x509 -text
+! host $fqdn > /dev/null && echo "$fqdn is not a vaild host." && exit 1
+echo "" | openssl s_client -servername $fqdn -connect $fqdn:$port 2>/dev/null | openssl x509 -text