Githubactions: Centos7: Replace repo mirror

.github/workflows/build_centos.yml

@@ -33,6 +33,13 @@ jobs:
           cat /etc/yum.repos.d/CentOS-Base.repo
           echo "--------------"
           cat /etc/yum.repos.d/CentOS-Vault.repo
+          
+          sed -i s/mirror.centos.org/vault.centos.org/g /etc/yum.repos.d/*.repo
+          sed -i s/^#.*baseurl=http/baseurl=http/g /etc/yum.repos.d/*.repo
+          sed -i s/^mirrorlist=http/#mirrorlist=http/g /etc/yum.repos.d/*.repo
+          
+          yum -y update
+          yum -y install epel-release
 
       - name: clone the Yubico/yubihsm-shell repository
         run: |