[enh] add centos-7 to LXC images (#2118)

## What does this PR do?

To test centos-7 on non centos systems add centos-7 image to the LXC suite.

## Why is this change important?

PR #2112 adds centos-7 support to the install scripts

## How to test this PR locally?

`sudo ./utils/lxc.sh build searx-centos7`

utils/lxc-searx.env

@@ -31,6 +31,9 @@ lxc_set_suite_env() {
 
         # rolling releases see https://www.archlinux.org/releng/releases/
         "$LINUXCONTAINERS_ORG_NAME:archlinux"     "archlinux"
+
+        # EOL 30 June 2024
+        "$LINUXCONTAINERS_ORG_NAME:centos/7"      "centos7"
     )
 
     PUBLIC_URL="${PUBLIC_URL:-http://$(uname -n)/searx}"

utils/lxc.sh

@@ -57,7 +57,7 @@ echo 'Set disable_coredump false' >> /etc/sudo.conf
 # shellcheck disable=SC2034
 centos7_boilerplate="
 yum update -y
-yum install -y git curl wget hostname
+yum install -y git curl wget hostname sudo
 echo 'Set disable_coredump false' >> /etc/sudo.conf
 "