[dhcp_server] Set to build dhcp_server image in vs image (sonic-net#17340)

Currently in this repo would not build dhcp_server container image by default, which would cause that building issue for dhcp_server introduced by other modules cannot be noticed in time.
This PR is to set build dhcp_server container in vs image.

Author: yaqiangz

azure-pipelines.yml

@@ -50,7 +50,7 @@ stages:
   jobs:
   - template: .azure-pipelines/azure-pipelines-build.yml
     parameters:
-      buildOptions: 'USERNAME=admin SONIC_BUILD_JOBS=$(nproc) BUILD_MULTIASIC_KVM=y ${{ variables.VERSION_CONTROL_OPTIONS }}'
+      buildOptions: 'USERNAME=admin SONIC_BUILD_JOBS=$(nproc) BUILD_MULTIASIC_KVM=y INCLUDE_DHCP_SERVER=y ${{ variables.VERSION_CONTROL_OPTIONS }}'
       jobGroups:
       - name: vs
 

rules/config

@@ -153,7 +153,7 @@ INCLUDE_NAT = y
 INCLUDE_DHCP_RELAY = y
 
 # INCLUDE_DHCP_SERVER - build and install dhcp-server package
-INCLUDE_DHCP_SERVER = n
+INCLUDE_DHCP_SERVER ?= n
 
 # INCLUDE_P4RT - build docker-p4rt for P4RT support
 INCLUDE_P4RT = n