qa/cephfs: remove rhel from kclient mount override

And switch to ubuntu.

Signed-off-by: Venky Shankar <vshankar@redhat.com>

diff --git a/qa/cephfs/mount/kclient/overrides/distro/stock/rhel_8.yaml b/qa/cephfs/mount/kclient/overrides/distro/stock/rhel_8.yaml
deleted file mode 120000 (symlink)
index 133acf2..0000000
--- a/qa/cephfs/mount/kclient/overrides/distro/stock/rhel_8.yaml
+++ /dev/null
@@ -1 +0,0 @@
-.qa/distros/all/rhel_8.yaml
\ No newline at end of file

diff --git a/qa/cephfs/mount/kclient/overrides/distro/stock/ubuntu_latest.yaml b/qa/cephfs/mount/kclient/overrides/distro/stock/ubuntu_latest.yaml
new file mode 120000 (symlink)
index 0000000..8286654
--- /dev/null
+++ b/qa/cephfs/mount/kclient/overrides/distro/stock/ubuntu_latest.yaml
@@ -0,0 +1 @@
+.qa/distros/supported-all-distro/ubuntu_latest.yaml
\ No newline at end of file