fix array declaration for install_site

[chaen]

When running bash with -u, an array declared with declare -a is considered as unbound variable if you do not put anything in it. It is not if you declare the array with ()
Noticed while installing new EL9 machine.
I don't know why it was not spotted before

[dirac@lbvobox900 ~]$ set +u
[dirac@lbvobox900 ~]$ declare -a with_declare
[dirac@lbvobox900 ~]$ echo "${with_declare[@]}"

[dirac@lbvobox900 ~]$ echo "${#with_declare[@]}"
0
[dirac@lbvobox900 ~]$ with_parent=()
[dirac@lbvobox900 ~]$ echo "${with_parent[@]}"

[dirac@lbvobox900 ~]$ echo "${#with_parent[@]}"
0




[dirac@lbvobox900 ~]$ set -u
[dirac@lbvobox900 ~]$ declare -a with_declare
[dirac@lbvobox900 ~]$ echo "${with_declare[@]}"

[dirac@lbvobox900 ~]$ echo "${#with_declare[@]}"
-bash: with_declare: unbound variable
[dirac@lbvobox900 ~]$ with_parent=()
[dirac@lbvobox900 ~]$ echo "${with_parent[@]}"

[dirac@lbvobox900 ~]$ echo "${#with_parent[@]}"
0