Merge pull request #2623 from return42/fix-centos7

[fix] add package `which` to CentOS-7 boilerplate

utils/lxc.sh

@@ -58,7 +58,7 @@ echo 'Set disable_coredump false' >> /etc/sudo.conf
 # shellcheck disable=SC2034
 centos7_boilerplate="
 yum update -y
-yum install -y git curl wget hostname sudo
+yum install -y git curl wget hostname sudo which
 echo 'Set disable_coredump false' >> /etc/sudo.conf
 "