Adding the CFN_BOOTSTRAP_VIRTUALENV_PATH variable in cfn-hook-update.conf (#2758)

Ref: #2742

Co-authored-by: Himani Deshpande <himanidp@amazon.com>

Author: himani2411

cookbooks/aws-parallelcluster-environment/templates/cfn_bootstrap/cfn-hook-update.conf.erb

@@ -1,5 +1,5 @@
 [parallelcluster-update]
 triggers=post.update
 path=Resources.<%= @launch_template_resource_id %>.Metadata.AWS::CloudFormation::Init
-action=PATH=/usr/local/bin:/bin:/usr/bin:/opt/aws/bin; . /etc/profile.d/pcluster_cookbook_environment.sh; cfn-init -v --stack <%= @stack_id %> --resource <%= @launch_template_resource_id %> --configsets update --region <%= @region %> --url <%= @cloudformation_url %> --role <%= @cfn_init_role %>
+action=PATH=/usr/local/bin:/bin:/usr/bin:/opt/aws/bin; . /etc/profile.d/pcluster_cookbook_environment.sh; $CFN_BOOTSTRAP_VIRTUALENV_PATH/cfn-init -v --stack <%= @stack_id %> --resource <%= @launch_template_resource_id %> --configsets update --region <%= @region %> --url <%= @cloudformation_url %> --role <%= @cfn_init_role %>
 runas=root