overlay/014: correct comment relating to workdir reuse

overlay/014: correct comment relating to workdir reuse

Clarification: EBUSY is what you get when trying to use the same
upperdir/workdir with two different *concurent* overlayfs mounts.
The EBUSY case is independent of the inodes index feature.

This is not the case in this test, but rather the case of trying to
reuse the same workdir with different upper dirs on *subsequent*
overlayfs mounts.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>