use rpm -i instead of yum install for epel7
use rpm -i instead of yum install for epel7

On BaseOS CI systems, `yum install` for the epel7 rpm does not work.
Instead, use `rpm -i` which should work on any system.  We should not
need to use `yum install` here because the epel7 setup rpm does not have
additional dependencies.
In addition, the rpm download sometimes returns 403 - I think it is because
multiple tests run in parallel in BaseOS CI, resulting in too many
download attempts in too short a period of time - so introduce a retry
to mitigate the situation.

Signed-off-by: Rich Megginson <eddfb389174a82ceee7387bfddd9793f5b4725f4@redhat.com>

linux-system-roles/network,linux-system-roles/network,linux-system-roles/network