qa: test fio with multiple versions of NFS

qa: test fio with multiple versions of NFS

This is coming from https://tracker.ceph.com/issues/69347, basically fio fails in
teuthology with v4.2 but passes with older versions (like v4.1). v4.2 on local/QE
machines has worked fine. This needs RCA, looking at libcephfs logs, it doesn't
look like it's CephFS. A thorough probe is needed, hence adding YAMLs to test
fio with different versions which also helps testing ceph client with different
version of NFS to help trace any regression.

unset.yaml is basically 4.2 for now but That may change someday or the nfs linux
driver may soon "add" things beyond 4.2 without adding an explicit version bump.

Fixes: https://tracker.ceph.com/issues/70203
Signed-off-by: Dhairya Parmar <dparmar@redhat.com>
Co-authored-by: Patrick Donnelly <pdonnell@ibm.com>