[lldp]Fix lldp spawned after reboot when disabled (sonic-net#11080)

- Why I did it
When LLDP is disabled through feature command, it gets spawned after reboot.

- How I did it
In syncd.sh check if the service is enabled before spawning automatically during cold reboot.

- How to verify it
Disable lldp feature. Perform cold reboot and verify its not spawned.

files/scripts/syncd.sh

@@ -63,9 +63,13 @@ function waitplatform() {
     if [[ x"$BOOT_TYPE" = @(x"fast"|x"warm"|x"fastfast") ]]; then
         debug "LLDP service is delayed by a timer for better fast/warm boot performance"
     else
-        debug "Starting lldp service..."
-        /bin/systemctl start lldp
-        debug "Started lldp service"
+        lldp_state=$(systemctl is-enabled lldp.timer)
+        if [[ $lldp_state == "enabled" ]]
+        then
+            debug "Starting lldp service..."
+            /bin/systemctl start lldp
+            debug "Started lldp service"
+        fi
     fi
 }