Update RPM installation procedure in README.md

2 jobs for master in 6 minutes and 17 seconds (queued for 1 second)
Status Job ID Name Coverage
  Package
passed #237111
docker-centos7
job-centos7-rpm

00:05:42

 
  Test
passed #237112
docker-centos7
job-centos7-rpm-test

00:00:34