qa/cephfs: make file data unique in caps_helper.py

qa/cephfs: make file data unique in caps_helper.py

Let's change the file data to include the file path, the CephFS name
and the host FS and CephFS mountpoint so that the bugs where, let's say,
"cephfs2" is mounted instead of "cephfs1" (where obviously both the
CephFSs lie on the same Ceph cluster) is caught by the tests due to
uniqueness of every test file's content.

Signed-off-by: Rishabh Dave <ridave@redhat.com>