Description of problem:
$releasever for RHEL-7 generated by yum is (for the workstation version) 7Workstation. Which is what most yum repositories expect (e.g., 
http://file.rdu.redhat.com/engdesktop/repo/libreoffice-csb/). However, dnf obviously generates 7.3 which breaks a lot of yum repos inclduing (it seems to me) RHN:

matej@mitmanek: ~$ sudo dnf update
Failed to synchronize cache for repo 'rhel-workstation-rhscl-7-beta-rpms' from 'https://cdn.redhat.com/content/beta/rhel/workstation/7/x86_64/rhscl/1/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-rh-common-rpms' from 'https://cdn.redhat.com/content/dist/rhel/workstation/7/7.3/x86_64/rh-common/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-optional-rpms' from 'https://cdn.redhat.com/content/dist/rhel/workstation/7/7.3/x86_64/optional/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-fastrack-rpms' from 'https://cdn.redhat.com/content/fastrack/rhel/workstation/7/x86_64/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-beta-rpms' from 'https://cdn.redhat.com/content/beta/rhel/workstation/7/x86_64/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-debug-rpms' from 'https://cdn.redhat.com/content/dist/rhel/workstation/7/7.3/x86_64/debug': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-optional-debug-rpms' from 'https://cdn.redhat.com/content/dist/rhel/workstation/7/7.3/x86_64/optional/debug': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-optional-beta-rpms' from 'https://cdn.redhat.com/content/beta/rhel/workstation/7/x86_64/optional/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-optional-fastrack-rpms' from 'https://cdn.redhat.com/content/fastrack/rhel/workstation/7/x86_64/optional/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'chromium' from 'http://install.linux.ncsu.edu/pub/yum/itecs/public/chromium/7.3/': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-rh-common-beta-rpms' from 'https://cdn.redhat.com/content/beta/rhel/workstation/7/x86_64/rh-common/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-htb-rpms' from 'https://cdn.redhat.com/content/htb/rhel/workstation/7/x86_64/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-extras-htb-rpms' from 'https://cdn.redhat.com/content/htb/rhel/workstation/7/x86_64/extras/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-beta-debug-rpms' from 'https://cdn.redhat.com/content/beta/rhel/workstation/7/x86_64/debug': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-extras-rpms' from 'https://cdn.redhat.com/content/dist/rhel/workstation/7/7Workstation/x86_64/extras/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-workstation-rhscl-7-rpms' from 'https://cdn.redhat.com/content/dist/rhel/workstation/7/7.3/x86_64/rhscl/1/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-supplementary-rpms' from 'https://cdn.redhat.com/content/dist/rhel/workstation/7/7.3/x86_64/supplementary/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-extras-debug-rpms' from 'https://cdn.redhat.com/content/dist/rhel/workstation/7/7Workstation/x86_64/extras/debug': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'rhel-7-workstation-rpms' from 'https://cdn.redhat.com/content/dist/rhel/workstation/7/7.3/x86_64/os': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Failed to synchronize cache for repo 'beaker-client' from 'http://download.lab.bos.redhat.com/beakerrepos/client/RedHatEnterpriseLinux7.3/': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried, disabling.
Using metadata from Mon Jun 13 21:39:37 2016
Dependencies resolved.
Nothing to do.
matej@mitmanek: ~$


Version-Release number of selected component (if applicable):
dnf-0.6.4-2.el7.noarch

How reproducible:
100%

Steps to Reproduce:
1.see above
2.
3.

Actual results:


Expected results:


Additional info: