Version pinning and enableing the upgrade role to run at all times

• pinning Versions of MLX, Kernel and lustre in CICD/vars/vars.yml
• a lot of magic on yum update * exclude versioned-stuffs in roles/upgrade/tasks/main.yml
• trigger yum cache refreshing on repository changes e.g. enabling centos-staging in config_repos
• bugfixes on testlustre ( whamcloud stopped publishing centos 77 rpms
• refactoring etcHosts role. not supporting ansible_domain anymore. ansible_fqdn would also only work after a reboot
• big refactor on mellanox_driver role. This now works perfectly for m3a010 and the two specified driver versions. The issue was kmod-mlnx-ofa_kernel.x86_64 4.5-OFED.4.5.1.0.1.1.gb4fdfac.rhel7u6 vs MELLANOX_VERSION: 4.5-OFED.4.5.1.0.1.1.gb4fdfac
• pulling because it was not reviewed timely
• pulling because it was not reviewed timely
• replacing usage of ansible_fqdn and ansible_domain from postix role
• pulling main logic from m3_force_upgrade into upgrade and ensuring this only happens if the kernel is going to change which is only allowed if the pinned version from vars/vars.yml is changing
• consistent use of reboot module ( it works great ! )

CICD/plays/testlustre/lustre.repo

 [lustre-server]
 name=lustre-server
-baseurl=https://downloads.whamcloud.com/public/lustre/latest-release/el7.7.1908/server
+baseurl=https://downloads.whamcloud.com/public/lustre/latest-release/el7/server
 # exclude=*debuginfo*
 gpgcheck=0
 
 [lustre-client]
 name=lustre-client
-baseurl=https://downloads.whamcloud.com/public/lustre/latest-release/el7.7.1908/client
+baseurl=https://downloads.whamcloud.com/public/lustre/latest-release/el7/client
 # exclude=*debuginfo*
 gpgcheck=0