[swss] Reduce Calls to SONiC Cfggen (sonic-net#5177)

Calls to sonic-cfggen is CPU expensive. This PR reduces calls to
sonic-cfggen to one call during startup when starting swss service.

singed-off-by: Tamer Ahmed <tamer.ahmed@microsoft.com>

dockers/docker-orchagent/docker-init.sh

@@ -2,18 +2,23 @@
 
 mkdir -p /etc/swss/config.d/
 
-sonic-cfggen -d -y /etc/sonic/sonic_version.yml -t /usr/share/sonic/templates/switch.json.j2 > /etc/swss/config.d/switch.json
-sonic-cfggen -d -t /usr/share/sonic/templates/ipinip.json.j2 > /etc/swss/config.d/ipinip.json
-sonic-cfggen -d -t /usr/share/sonic/templates/ports.json.j2 > /etc/swss/config.d/ports.json
-sonic-cfggen -d -t /usr/share/sonic/templates/copp.json.j2 > /etc/swss/config.d/00-copp.config.json
+CFGGEN_PARAMS=" \
+    -d \
+    -y /etc/sonic/constants.yml \
+    -t /usr/share/sonic/templates/switch.json.j2,/etc/swss/config.d/switch.json \
+    -t /usr/share/sonic/templates/ipinip.json.j2,/etc/swss/config.d/ipinip.json \
+    -t /usr/share/sonic/templates/ports.json.j2,/etc/swss/config.d/ports.json \
+    -t /usr/share/sonic/templates/copp.json.j2,/etc/swss/config.d/00-copp.config.json \
+    -t /usr/share/sonic/templates/vlan_vars.j2 \
+"
+VLAN=$(sonic-cfggen $CFGGEN_PARAMS)
 
 # Executed HWSKU specific initialization tasks.
 if [ -x /usr/share/sonic/hwsku/hwsku-init ]; then
     /usr/share/sonic/hwsku/hwsku-init
 fi
 
 # Start arp_update when VLAN exists
-VLAN=`sonic-cfggen -d -v 'VLAN.keys() | join(" ") if VLAN'`
 if [ "$VLAN" != "" ]; then
     cp /usr/share/sonic/templates/arp_update.conf /etc/supervisord/conf.d/
 fi

dockers/docker-orchagent/vlan_vars.j2

@@ -0,0 +1 @@
+{%- if VLAN -%}{{- VLAN.keys() | join(' ') -}}{%- endif -%}