mcastmngr: Make sure we don't crash during boot up.

Avoid polluting the syslog with messages regarding
mcastmngr crashing:

procd: Instance mcast::instance1 s in a crash loop 6 crashes, 0 seconds since last crash

mcastmngr/files/broadcom/lib/mcast/broadcom.sh

@@ -251,3 +251,7 @@ configure_mcast() {
 
 	configure_mcpd
 }
+
+validate_params() {
+	return 0
+}

mcastmngr/files/common/etc/init.d/mcast

@@ -33,6 +33,10 @@ start_service() {
 		configure_mcast
 	fi
 
+	if ! validate_params; then
+		return
+	fi
+
 	if [ -z "${PROG_PARAMS}" ]; then
 		start_mcast_service
 	else

mcastmngr/files/linux/lib/mcast/linux.sh

@@ -425,3 +425,9 @@ configure_mcast() {
 	read_mcast_proxy_params
 	config_mcproxy
 }
+
+validate_params() {
+	[ -n "${PROG_PARAMS}" ] && return 0
+
+	return 1
+}