test: Clean up skips in check-storage-vdo
test: Clean up skips in check-storage-vdo

Don't run the legacy and package install tests on non-RHEL/CentOS at
all. Logging in and immediately skipping the test is just a waste of
time.

Also generalize them to apply to all RHEL 8.y versions.

martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,mvollmer/cockpit