RHEL7.4: install packages in one yum instance

Currently we are opening and closing a yum instance for every package
we install during provisioning. This is a bit inefficient so it's
better to install them in one go.

Task-number: QTQAINFRA-1586
Change-Id: Idbf814f9023da0fe8213b2ed84cd1a27a149fc27
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@qt.io>