Fix for CentOS 8

- The repository ID "powertools" is now lower case in the latest
  CentOS release. Update to work in both cases.

extras/vpnupgrade_centos.sh

@@ -144,7 +144,7 @@ yum -y install nss-devel nspr-devel pkgconfig pam-devel \
 
 REPO1='--enablerepo=*server-*optional*'
 REPO2='--enablerepo=*releases-optional*'
-REPO3='--enablerepo=PowerTools'
+REPO3='--enablerepo=[Pp]ower[Tt]ools'
 
 if grep -qs "release 7" /etc/redhat-release; then
   yum -y install systemd-devel || exiterr2

vpnsetup_centos.sh

@@ -147,7 +147,7 @@ bigecho "Installing packages required for the VPN..."
 REPO1='--enablerepo=epel'
 REPO2='--enablerepo=*server-*optional*'
 REPO3='--enablerepo=*releases-optional*'
-REPO4='--enablerepo=PowerTools'
+REPO4='--enablerepo=[Pp]ower[Tt]ools'
 
 yum -y install nss-devel nspr-devel pkgconfig pam-devel \
   libcap-ng-devel libselinux-devel curl-devel nss-tools \