cephfs: fix tracevol.py to work with dynamic value of fsname
cephfs: fix tracevol.py to work with dynamic value of fsname

tracevol.py takes 'myfs' as default fsname, changed it so that it can work with
dynamic values of fsname.

Signed-off-by: Mudit Agarwal <e5356c34e3b3b8ef2f9750bb431df6fcd5e2fa6e@redhat.com>

ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi